docs: Add documenation for OpenTofu support (#42448)

Closes -

Release Notes:

- N/A

Signed-off-by: Tom Zaspel <40226087+tzabbi@users.noreply.github.com>

docs/src/SUMMARY.md

@@ -126,6 +126,7 @@
 - [Markdown](./languages/markdown.md)
 - [Nim](./languages/nim.md)
 - [OCaml](./languages/ocaml.md)
+- [OpenTofu](./languages/opentofu.md)
 - [PHP](./languages/php.md)
 - [PowerShell](./languages/powershell.md)
 - [Prisma](./languages/prisma.md)

docs/src/languages/opentofu.md

@@ -0,0 +1,20 @@
+# OpenTofu
+
+OpenTofu support is available through the [OpenTofu extension](https://github.com/ashpool37/zed-extension-opentofu).
+
+- Tree-sitter: [MichaHoffmann/tree-sitter-hcl](https://github.com/MichaHoffmann/tree-sitter-hcl)
+- Language Server: [opentofu/tofu-ls](https://github.com/opentofu/tofu-ls)
+
+## Configuration
+
+In order to automatically use the OpenTofu extension and language server when editing .tf and .tfvars files,
+either uninstall the Terraform extension or add this to your settings.json:
+
+```json
+"file_types": {
+  "OpenTofu": ["tf"],
+  "OpenTofu Vars": ["tfvars"]
+},
+```
+
+See the [full list of server settings here](https://github.com/opentofu/tofu-ls/blob/main/docs/SETTINGS.md).