* Make `:write` create nonexistent subdirectories
Prompting as to whether this should take place remains a TODO.
* Move subdirectory creation to new `w!` command
* Add runtime language configuration (#1794)
* Add set-language typable command to change the language of current buffer.
* Add completer for available language options.
* Update set-language to refresh language server as well
* Add language id based config lookup on `syntax::Loader`.
* Add `Document::set_language3` to set programming language based on language
id.
* Update `Editor::refresh_language_server` to try language detection only if
language is not already set.
* Remove language detection from Editor::refresh_language_server
* Move document language detection to where the scratch buffer is saved.
* Rename Document::set_language3 to Document::set_language_by_language_id.
* Remove unnecessary clone in completers::language
This is a rather large refactor that moves most of the code for
loading, fetching, and building grammars into a new helix-loader
module. This works well with the [[grammars]] syntax for
languages.toml defined earlier: we only have to depend on the types
for GrammarConfiguration in helix-loader and can leave all the
[[language]] entries for helix-core.