rc jinja: Highlight Jinja statements/expressions

This commit implements a standalone shared highlighter group that
highlights Jinja statements and expressions.

The traditional way of highlighting file contents is to hook on the
file extension, and assign a custom filetype/highlighter group to
the current buffer. However, since Jinja templates can be based on
any text file format in existence, we do not have a specific file
extension to hook, and consequently, no custom "jinja" filetype.

The user is expected to add the `jinja` highlighter whenever required:

```
require-module jinja
add-highlighter window/ ref jinja
```

Alternatively, file extensions that are known to occasionally pair
with Jinja can be hooked from the user configuration:

```
hook global WinCreate .+\.html %[
    try %[
        execute-keys -draft \%s \{%|\{\{ <ret>
        require-module jinja
        add-highlighter window/ ref jinja
    ]
]
```

The above hook auto-detects statements/expressions (respectively
{%…%} and {{…}} expansions), but will cause false positives
(in terms of highlighting), and therefore isn't part of `jinja.kak`
by default.

rc/filetype/jinja.kak

@@ -0,0 +1,35 @@
+# https://palletsprojects.com/p/jinja/
+# ‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
+
+provide-module jinja %[
+
+require-module python
+
+# Highlighters
+# ‾‾‾‾‾‾‾‾‾‾‾‾
+
+add-highlighter shared/jinja regions
+add-highlighter shared/jinja/comment region '\{#' '#\}' fill comment
+
+# TODO: line statements # …
+
+add-highlighter shared/jinja/statement region '\{%' '%\}' group
+add-highlighter shared/jinja/statement/ ref python
+add-highlighter shared/jinja/statement/ regex \{%[+-]?|[+-]?%\} 0:value
+add-highlighter shared/jinja/statement/tests regex \b(callable|even|le|none|string|defined|ge|lower|number|undefined|divisibleby|gt|lt|odd|upper|eq|in|mapping|sameas|escaped|iterable|ne|sequence)\b 0:builtin
+add-highlighter shared/jinja/statement/functions regex \b(range|lipsum)\b 0:function
+add-highlighter shared/jinja/statement/macro regex \b(((end)?(call|macro)))\b 0:keyword
+add-highlighter shared/jinja/statement/extensions regex \b(((end)?(block|trans))|(pluralize))\b 0:keyword
+add-highlighter shared/jinja/statement/control regex \b(((end)?(if|for|with))|(break|continue))\b 0:keyword
+add-highlighter shared/jinja/statement/filters regex \b(?:(?:(filter)\s+|\|\s*)(abs|attr|batch|capitalize|center|default|dictsort|e|escape|filesizeformat|first|float|forceescape|format|groupby|indent|int|join|last|length|list|lower|map|max|min|pprint|random|reject|rejectattr|replace|reverse|round|safe|select|selectattr|slice|sort|string|striptags|sum|title|tojson|trim|truncate|unique|upper|urlencode|urlize|wordcount|wordwrap|xmlattr)|(endfilter))\b 1:keyword 3:keyword 2:builtin
+add-highlighter shared/jinja/statement/ regex \b((end)?(autoescape|raw|set))\b 0:keyword
+add-highlighter shared/jinja/statement/ regex \b(do|extends|include)\b 0:keyword
+add-highlighter shared/jinja/statement/ regex \bignore\s+missing\b 0:meta
+add-highlighter shared/jinja/statement/ regex \bwith(out)?\s+context\b 0:meta
+
+add-highlighter shared/jinja/expression region '\{\{' '\}\}' group
+add-highlighter shared/jinja/expression/ ref python
+add-highlighter shared/jinja/expression/ regex \{\{|\}\} 0:value
+add-highlighter shared/jinja/expression/filters regex \|\s*(abs|attr|batch|capitalize|center|default|dictsort|e|escape|filesizeformat|first|float|forceescape|format|groupby|indent|int|join|last|length|list|lower|map|max|min|pprint|random|reject|rejectattr|replace|reverse|round|safe|select|selectattr|slice|sort|string|striptags|sum|title|tojson|trim|truncate|unique|upper|urlencode|urlize|wordcount|wordwrap|xmlattr)\b 1:builtin
+
+]