Add CodeSandbox Theme (zed-industries#775)

This PR brings the [CodeSandbox theme from
VSCode](https://marketplace.visualstudio.com/items?itemName=CodeSandbox-io.codesandbox-projects-theme)
over to Zed, done using Zed's tool to convert VSCode themes. Works great
from my testing. It has been requested
[here](zed-industries#544).

I have no affiliation with CodeSandbox in any way, hence the mentions of
this theme being unofficial.

I request this theme to be merged into the extensions repo and made
available through the extensions store by the maintainers. Any feedback
highly appreciated!

![screen 2024-05-22 at 21 37
50](https://github.com/zed-industries/extensions/assets/32536904/9e707abc-f7f8-40e3-9788-843e38243cd6)

---------

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

.gitmodules

@@ -90,6 +90,10 @@
 	path = extensions/cfengine
 	url = https://github.com/olehermanse/zed-cfengine.git
 
+[submodule "extensions/codesandbox-theme"]
+	path = extensions/codesandbox-theme
+	url = https://github.com/MartinRybergLaude/zed-theme-codesandbox.git
+
 [submodule "extensions/colorizer"]
 	path = extensions/colorizer
 	url = https://github.com/tamimhasandev/colorizer.git

extensions.toml

@@ -101,6 +101,10 @@ submodule = "extensions/zed"
 path = "extensions/clojure"
 version = "0.0.2"
 
+[codesandbox-theme]
+submodule = "extensions/codesandbox-theme"
+version = "0.0.1"
+
 [colorizer]
 submodule = "extensions/colorizer"
 version = "0.0.3"