Supports
https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_onTypeFormatting

rust-analyzer uses this feature to add matching brackets semantically,
e.g.
before:
![Screenshot 2023-05-23 at 17 46
42](https://github.com/zed-industries/zed/assets/2690773/020e8448-23e6-4a38-8dbb-c9edf18062f7)

after:
![Screenshot 2023-05-23 at 17 46
49](https://github.com/zed-industries/zed/assets/2690773/4d140af3-aca6-451d-ac61-e2a9bb31caea)

`use_on_type_format` settings entry was added, enabled by default, to
disable the new feature.

Release Notes:

* Support `OnTypeFormatting` LSP protocol feature, allowing
rust-analyzer to add matching brackets