Add icon for KDL files (#35377)

<img width="191" height="83" alt="1753920601"
src="https://github.com/user-attachments/assets/6bf057b0-2f10-4cc7-bab1-2d4aa8675701"
/>

Release Notes:

- Added icon for KDL (`.kdl`) files

crates/theme/src/icon_theme.rs

@@ -152,6 +152,7 @@ const FILE_SUFFIXES_BY_ICON_KEY: &[(&str, &[&str])] = &[
     ("javascript", &["cjs", "js", "mjs"]),
     ("json", &["json"]),
     ("julia", &["jl"]),
+    ("kdl", &["kdl"]),
     ("kotlin", &["kt"]),
     ("lock", &["lock"]),
     ("log", &["log"]),
@@ -315,6 +316,7 @@ const FILE_ICONS: &[(&str, &str)] = &[
     ("javascript", "icons/file_icons/javascript.svg"),
     ("json", "icons/file_icons/code.svg"),
     ("julia", "icons/file_icons/julia.svg"),
+    ("kdl", "icons/file_icons/kdl.svg"),
     ("kotlin", "icons/file_icons/kotlin.svg"),
     ("lock", "icons/file_icons/lock.svg"),
     ("log", "icons/file_icons/info.svg"),