Function calls and format specifier are not printed correctly.
Usually people are using `faith/vim-go` to group these highlights.
We add the corresponding color the vim-go groups. Still there
are some groups that are not present/defined in vim-go. I've added
a comment there for future fix.

Signed-off-by: hoenirvili <hoenirvili@gmail.com>

Neovim version 0.5 [1] is a long-time awaited update that introduces
features like tree-sitter [2][3] support and native LSP [4][5].
Even though Neovim devides more and more from Vim through specific
features like first-class Lua support with custom APIs, the highlighting
for tree-sitter is achived through "normal" syntax highlighting groups.
Most of the groups are already linked by the nvim-treesitter plugin by
default [6] so only a few groups have been adjuated for now to fit the
Nord style.

[1]: https://github.com/neovim/neovim/releases/tag/v0.5.0
[2]: https://github.com/tree-sitter/tree-sitter
[3]: https://github.com/nvim-treesitter/nvim-treesitter
[4]: https://neovim.io/doc/user/lsp.html
[5]: https://github.com/neovim/nvim-lspconfig
[6]: https://github.com/nvim-treesitter/nvim-treesitter/blob/90f15d9/plugin/nvim-treesitter.vim

Co-authored-by: Ferran Jovell <ferran.jovell@gmail.com>
Co-authored-by: Arctic Ice Studio <development@arcticicestudio.com>
Co-authored-by: Sven Greb <development@svengreb.de>

Closes nordthemeGH-235

Add support for `vim-pandoc/vim-pandoc-syntax`

To improve syntax highlighting for Pandoc [1], support for the
vim-pandoc/vim-pandoc-syntax [2] plugin has been implemented.
Most groups are linked to existing Markdown groups to ensure a
consistent style across languages and different plugins.

Configurations used for testing:

```vim
let g:pandoc#syntax#conceal#cchar_overrides = {"atx": "〉"}
let g:nord_italic = 1
```

Resources:

- `g:pandoc#syntax#conceal#cchar_overrides` docs [3]
- `s:cchars` definition [4]
- Markdown "Extended Syntax" Guide [5]

[1]: https://pandoc.org
[2]: https://github.com/vim-pandoc/vim-pandoc-syntax
[3]: https://github.com/vim-pandoc/vim-pandoc-syntax/blob/68d7249/doc/pandoc-syntax.txt#L45-L50
[4]: https://github.com/vim-pandoc/vim-pandoc-syntax/blob/5056e63/syntax/pandoc.vim#L37-L72
[5]: https://www.markdownguide.org/extended-syntax

Co-authored-by: Arctic Ice Studio <development@arcticicestudio.com>
Co-authored-by: Sven Greb <development@svengreb.de>

Closes nordthemeGH-220

Support for LSP code lenses

Before LSP code lenses [1] where code lenses were highlighted with the
default color which has been changed to make it less visually intrusive,
like other UI related elements, i.e. messages of linters.

[1]: https://neovim.io/doc/user/lsp.html#lsp-highlight-codelens

nordthemeGH-266


Co-authored-by: Arctic Ice Studio <development@arcticicestudio.com>

The `TSError` group is used to highlight syntax/parser errors [1] which
caused an aggressive styling where the background color of many syntax
elements was rendered with `nord11` during typing. This was caused due
to the fast processing of `tree-sitter` which also resulted in highlight
flickering.
This is a known problem and was fixed by many other themes (e.g. Dracula
[2]) by removing the group again. One of the core maintainers of
`nvim-treesitter` provided a solution by remapping groups [3] and also
mentioned that the group is styled by the `nvim-treesitter` plugin but
the active theme [4].

Syntax errors can still be highlighted through linters and parsers like
Neovim's LSP [5] can still be used instead to highlight errors with the
correct style (e.g. only change the foreground color of a single word).

[1]: https://github.com/nvim-treesitter/nvim-treesitter/blob/fb5d6e04/doc/nvim-treesitter.txt#L493-L495
[2]: dracula/vim#232
[3]: nvim-treesitter/nvim-treesitter#78 (comment)
[4]: nvim-treesitter/nvim-treesitter#1016 (comment)
[5]: https://github.com/neovim/nvim-lspconfig

Fixes nordthemeGH-269

…me#282)

In Neovim `0.6.0` [1] the naming scheme for the highlight groups of the
diagnostic API changed [2]. The new groups have been added as default while
the previous groups are conditionally guarded when using Neovim `0.5.0`.

[1]: https://github.com/neovim/neovim/releases/tag/v0.6.0
[2]: neovim/neovim@a5bbb93#diff-51fab2b766d0a3b606462e95de492190df173b7296147912307cdad636cd492aR77


Co-authored-by: Arctic Ice Studio <development@arcticicestudio.com>
Co-authored-by: Sven Greb <development@svengreb.de>

nordthemeGH-282

Support for Neovim LSP `documentHighlight` groups

The Neovim LSP `textDocument` / `documentHightlight` groups [1] are
responsible to highlight tokens in a document that are related to each
other, e.g. decalred variables, using the
`vim.buf.lsp.document_highlight()` function.
Also see the LSP specification about "Document Highlights Request" [2]
for more details.

[1]: https://github.com/neovim/neovim/blob/f92a2457c2e7ad14d9a5a907ef4213fa770b6d95/runtime/doc/lsp.txt#L423
[2]: https://microsoft.github.io/language-server-protocol/specification#textDocument_documentHighlight


Co-authored-by: Arctic Ice Studio <development@arcticicestudio.com>
Co-authored-by: Sven Greb <development@svengreb.de>

Improve readability of C language constants

To improve the readability of C language constants, defined by the
`cConstant` syntax highlighting group [1], these are now colored with
`nord9` for the foreground to make them stand out. This is important in
C, since interesting things are usually happening in their proximity,
like checking/returning an error, passing particular values/flags to
functions and so on.

[1]: https://github.com/vim/vim/blob/0e6adf8a29d5c2c96c42cc7157f71bf22c2ad471/runtime/syntax/c.vim#L313-L375



Co-authored-by: Arctic Ice Studio <development@arcticicestudio.com>
Co-authored-by: Sven Greb <development@svengreb.de>

nordthemeGH-283

The `vim.lsp.buf.signature_help` function is used to highlight the
active parameter in the signature help [1].
Before this commit the active parameter was not styled differently to
any other parameter which made it hard to distinguish it. This has been
improved by adding support for the `LspSignatureActiveParameter` syntax
highlighting group where the active parameter now uses `nord8` are
foreground color and additionally a font underline with the same color.

[1]: https://github.com/neovim/neovim/blob/70db972e5fbcab39946ad8ac05472a693cf65b68/runtime/doc/lsp.txt#L456-L459


Co-authored-by: Sven Greb <development@svengreb.de>
Co-authored-by: Arctic Ice Studio <development@arcticicestudio.com>

nordthemeGH-286

Signed-off-by: hoenirvili <hoenirvili@gmail.com>