* Add command for merging non-consecutive ranges
* Add `merge_selections` command to book
* Simplify `merge_ranges`
Heeded the advice of @the-mikedavis to stop iterating over all ranges and simply merge the first and the last range, as the invariants of `Selection` guarantee that the list of ranges is always sorted and never empty.
* Clarify doc comment of `merge_ranges`
* Add `helix_lsp::client::Client::supports_feature(&self, LanguageServerFeature)`
* Extend `doc.language_servers_with_feature` to use this method as filter as well
* Add macro `language_server_with_feature!` to reduce boilerplate for non-mergeable language server requests (like goto-definition)
* Refactored most of the `find_map` code to use the either the macro or filter directly via `doc.language_servers_with_feature`
Language Servers are now configured in a separate table in `languages.toml`:
```toml
[langauge-server.mylang-lsp]
command = "mylang-lsp"
args = ["--stdio"]
config = { provideFormatter = true }
[language-server.efm-lsp-prettier]
command = "efm-langserver"
[language-server.efm-lsp-prettier.config]
documentFormatting = true
languages = { typescript = [ { formatCommand ="prettier --stdin-filepath ${INPUT}", formatStdin = true } ] }
```
The language server for a language is configured like this (`typescript-language-server` is configured by default):
```toml
[[language]]
name = "typescript"
language-servers = [ { name = "efm-lsp-prettier", only-features = [ "format" ] }, "typescript-language-server" ]
```
or equivalent:
```toml
[[language]]
name = "typescript"
language-servers = [ { name = "typescript-language-server", except-features = [ "format" ] }, "efm-lsp-prettier" ]
```
Each requested LSP feature is priorized in the order of the `language-servers` array.
For example the first `goto-definition` supported language server (in this case `typescript-language-server`) will be taken for the relevant LSP request (command `goto_definition`).
If no `except-features` or `only-features` is given all features for the language server are enabled, as long as the language server supports these. If it doesn't the next language server which supports the feature is tried.
The list of supported features are:
- `format`
- `goto-definition`
- `goto-declaration`
- `goto-type-definition`
- `goto-reference`
- `goto-implementation`
- `signature-help`
- `hover`
- `document-highlight`
- `completion`
- `code-action`
- `workspace-command`
- `document-symbols`
- `workspace-symbols`
- `diagnostics`
- `rename-symbol`
- `inlay-hints`
Another side-effect/difference that comes with this PR, is that only one language server instance is started if different languages use the same language server.
