Add gem extension (#1628)

Improve the development experience of writing
[Gem](https://github.com/mantou132/gem) elements.

- inline HTML/CSS/Style snippets
- inline HTML/CSS highlight support // extend zed typescript
- inline HTML/CSS hover info
- inline HTML/CSS auto completion

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

.gitmodules

@@ -458,6 +458,10 @@
 	path = extensions/gdscript
 	url = https://github.com/GDQuest/zed-gdscript.git
 
+[submodule "extensions/gem"]
+	path = extensions/gem
+	url = https://github.com/mantou132/gem
+
 [submodule "extensions/gemini"]
 	path = extensions/gemini
 	url = https://github.com/clseibold/gemini-zed.git

extensions.toml

@@ -499,6 +499,11 @@ version = "0.3.0"
 submodule = "extensions/gdscript"
 version = "0.4.0"
 
+[gem]
+submodule = "extensions/gem"
+path = "crates/zed-plugin-gem"
+version = "0.0.1"
+
 [gemini]
 submodule = "extensions/gemini"
 version = "0.0.1"