Improve readability.

This commit...

1. fixes duplicated meta.tag scopes in `<template>` tags
2. fixes missing meta.tag scope at the closing `>` in `<template>` tags
3. adds syntax tests for template tags

This commit fixes implementation of mustage template tags {{...}}.

Before this commit they tried to pop the `main` context off stack
and caused `template-tag-content` to never have been popped off stack
properly.

With this commit the syntax distinguishes between embedded template
tags and those which interpolate strings. The latter one remove
`string` scope for better highlighting java code in `{{ ... }}`.

It also does no longer push a dedicated `mustage-content` context on
stack as this is the same content as the whole document. It's not
required.

All `v-foo` directive attributes have not been scoped
`meta-attribute-with-value` which effects syntax highlighting when
using certain color schemes. That's fixed by this commit.

Note: It appears YAMLmacros sorts generated output randomly, so many
changes of the generated sublime-syntax file can be ignored.

This commit refactors close-tag context handling in order to fix meta
scopes of stray closing tags.

Before this commit they received the default meta and entity scope from
HTML.sublime-syntax. This may result in inconsistent highlighting once
they are directly addressed by a color scheme.

That's a fix which is planned for core HTML.sublime-syntax, too.
The change of `script-tag` and `style-tag` also fixes duplicated
meta.tag scopes for script/style tags for ST builds before 4114.

This commit just moves sections/contexts around. It doesn't change
behavior.

The goal is to end up with the same order as HTML.sublime-syntax which
uses a top-down-order.

1. managing contexts
2. tag contexts
3. attribute contexts
4. other reusable contexts
5. prototypes

applies sublimehq/Packages#2430

All sublime-syntax version 2 files should use explicit `pop: 1` instead
of `pop: true`. It looks more consistent in case `pop: 2` are used.

No need to duplicate the match directive if it already exists.

This commit fixes sublimehq/Packages#2910 for
all ST builds before 4114.

ST's HTML.sublime-syntax may change in the future so that the change of
this commit is required to maintain compatibility. It is planned to
highlight certain self-closing tags illegal, if they are known not to
support it.

This change is backward compatible with older builds of ST4.

Addresses #216 (comment)

This commit includes `JavaScript#expression-statement` context in
attribute/directive values to highlight mappings correctly.

The `pop: 1` is removed as the included context pops itself off stack.

Run YAML macros in python 3.8 in order to maintain dictionary key sort
order.

This allows easily targeting the embed scopes inside attributes as
something that is contributed and supported by the vue syntax only as
opposed to a a `<script>` tag which uses HTML syntax.

Use vue suffix for embed_scope in attributes and mustache

This commit moves terminating patterns to the top so they match with
max priority in case of overlapping patterns. This change is just to
be future proof if core HTML syntax changes.

This commit follows a scope naming scheme introduced to Astro, Blade, Liquid, PHP and Slim recently, which uses

1. `meta.embedded.<template-name>` for those template code sections,
   which are used for control structures primarily.

   This scope has already been in use in PHP syntax to scope all
   `<?php ... ?>` code sections.

2. `meta.interpolation.<template-name>` for those template code
    sections, which primarily emit data to the output document.

    That's what Mustage tags `{{ expr }}` do primarily.

1. extend `meta.interpolation` to include leading and trailing
   punctuation to comply with ST's scope naming guidelines.
2. fix closing `]` scope.
3. adjust/add tests