docs: update to rewrite

This updates

* README
* CONTRIBUTING
* the `:h nvim-treesitter` documentation

to the current state of `main`. It also adds a pull request template for
adding a new language.

.github/PULL_REQUEST_TEMPLATE/new_language.md

@@ -0,0 +1,45 @@
+<!-- 
+  Before proceeding, make sure you have read https://github.com/nvim-treesitter/nvim-treesitter/blob/main/CONTRIBUTING.md!
+  Make sure to fill out all fields and read the checklist at the end.
+-->
+
+# Name of language
+
+<!-- Link to an official description of the language -->
+https://...
+
+<details>
+<summary>Representative code sample</summary>
+```
+max. 50 lines
+```
+</details>
+
+## Parser repo
+
+https://github.com/...
+
+<details>
+<summary>Parsed tree for code sample</summary>
+```
+paste output of tree-sitter parse or :InspectTree here
+```
+</details>
+
+## Queries
+
+Source of queries: https://github.com/... (or "written from scratch")
+
+<details>
+<summary>Screenshots of code sample</summary>
+<!-- paste screenshot of code sample using provided queries here -->
+</details>
+
+<!--
+CHECKLIST: _Before_ submitting, make sure
+
+* `./scripts/install-parsers.lua <language>` works without warnings
+* `./scripts/install-parsers.lua --generate <language>` works without warnings
+* `make query` works without warning
+* `make docs` is run
+-->

.github/pull_request_template.md

@@ -0,0 +1,5 @@
+<!--
+  Before proceeding, make sure you have read https://github.com/nvim-treesitter/nvim-treesitter/blob/main/CONTRIBUTING.md!
+  If you are adding a new parser, use this link instead:
+  <https://github.com/nvim-treesitter/nvim-treesitter/compare/main...my-branch?quick_pull=1&template=new_language.md>
+-->