Add Sublime Mariana theme (#1356)

Theme, that imitates Sublime Text 4's Mariana theme.

The Mariana color scheme is known for its cool, muted tones that provide
a soothing yet vibrant coding environment, making it easy on the eyes
during long coding sessions. This theme avoids the use of _cursive or
italic_ styles, ensuring a consistent and clean look across all text
elements for enhanced readability and focus.

There are two distinct variations: `Sublime Mariana` and Sublime
Breakers. Theme variation closely mirrors the original, offering a cool,
muted color scheme that’s easy on the eyes.


![mariana-zed](https://github.com/user-attachments/assets/7f6c7f6b-eeb8-4e17-930b-74d65ec6c2e1)

> [!NOTE]  
> I’m aware that a [similar
theme](https://github.com/biaqat/mariana-theme-zed/tree/f5a79b6a20628a155c339d19e43a31719e0c7636)
already exists, but this version offers some key differences. Notably,
it contains only two color schemas and uses only the normal text style,
with no italic or bold elements, to provide a clean and uniform
appearance throughout. If you decide to decline this PR due to the
similar existing theme, no problem—just wanted to share an alternative
version!

Co-authored-by: Marshall Bowers <[email protected]>

.gitmodules

@@ -994,6 +994,10 @@
 	path = extensions/struct-theme
 	url = https://gitlab.com/Fake.User/struct-zed-theme
 
+[submodule "extensions/sublime-mariana-theme"]
+	path = extensions/sublime-mariana-theme
+	url = https://github.com/hnatiukr/zed-mariana-theme.git
+
 [submodule "extensions/surrealql"]
 	path = extensions/surrealql
 	url = https://github.com/siteforge-io/surql-zed

extensions.toml

@@ -1110,6 +1110,10 @@ version = "0.0.2"
 submodule = "extensions/struct-theme"
 version = "0.0.1"
 
+[sublime-mariana-theme]
+submodule = "extensions/sublime-mariana-theme"
+version = "1.1.0"
+
 [surrealql]
 submodule = "extensions/surrealql"
 version = "0.0.2"