feat(completion): add nvim-cmp-buffer-lines (#1056)

* feat(completion): add `nvim-cmp-buffer-lines`

* Update lua/astrocommunity/completion/nvim-cmp-buffer-lines/README.md

Co-authored-by: Uzair Aftab <48220549+Uzaaft@users.noreply.github.com>

* fix readme wording

* add note to readme

---------

Co-authored-by: Uzair Aftab <48220549+Uzaaft@users.noreply.github.com>

lua/astrocommunity/completion/nvim-cmp-buffer-lines/README.md

@@ -0,0 +1,7 @@
+# nvim-cmp-buffer-lines
+
+nvim-cmp source for buffer lines
+
+**Repository:** <https://github.com/amarakon/nvim-cmp-buffer-lines>
+
+_Replaces_ the `<C-x><C-l>` whole line complete, instead of being included in the usual completion menu.

lua/astrocommunity/completion/nvim-cmp-buffer-lines/init.lua

@@ -0,0 +1,27 @@
+---@type LazySpec
+return {
+  "hrsh7th/nvim-cmp",
+  dependencies = {
+    { "amarakon/nvim-cmp-buffer-lines" },
+  },
+  opts = function(_, opts)
+    local cmp = require "cmp"
+    return require("astrocore").extend_tbl(opts, {
+      mapping = {
+        ["<C-x><C-l>"] = cmp.mapping.complete { -- this could've been a more ergonomic hotkey, but it would be a reach to try to make up one, that would fit everyone.
+          config = {
+            sources = {
+              {
+                name = "buffer-lines",
+                priority = 50,
+                option = {
+                  leading_whitespace = false,
+                },
+              },
+            },
+          },
+        },
+      },
+    })
+  end,
+}