Extract candidates with variants in Clojure/ClojureScript keywords (#18338)

## Summary

Taking a shot at fixing my own complaint from #18336. 

Added failing test and fix for extracting classes containing a
pseudo-class from Clojure keywords. Eg., `:hover:text` ->
`"hover:text"`. This would previously produce `["hover", "text"]`.

## Test plan

- Add a failing test. 
- Verify that it fails with `cargo test`. 
- Add fix. 
- Verify that `cargo test` has no further complaints. 

ATT: @RobinMalfait

---------

Co-authored-by: Jordan Pittman <jordan@cryptica.me>

crates/oxide/src/extractor/pre_processors/clojure.rs

@@ -42,7 +42,7 @@ impl PreProcessor for Clojure {
                     }
                 }
 
-                // A `.`  surrounded by digits is a decimal number, so we don't want to replace it.
+                // A `.` surrounded by digits is a decimal number, so we don't want to replace it.
                 //
                 // E.g.:
                 // ```
@@ -54,6 +54,18 @@ impl PreProcessor for Clojure {
                     // Keep the `.` as-is
                 }
 
+                // A `:` surrounded by letters denotes a variant. Keep as is.
+                //
+                // E.g.:
+                // ```
+                // lg:pr-6"
+                //   ^
+                // ``
+                b':' if cursor.prev.is_ascii_alphanumeric() && cursor.next.is_ascii_alphanumeric() => {
+
+                    // Keep the `:` as-is
+                }
+
                 b':' | b'.' => {
                     result[cursor.pos] = b' ';
                 }
@@ -178,4 +190,16 @@ mod tests {
 
         Clojure::test_extract_contains(input, vec!["flex", "gap-1.5", "p-1"]);
     }
+
+    // https://github.com/tailwindlabs/tailwindcss/issues/18336
+    #[test]
+    fn test_extraction_of_pseudoclasses_from_keywords() {
+        let input = r#"
+            ($ :div {:class [:flex :first:lg:pr-6 :first:2xl:pl-6 :group-hover/2:2xs:pt-6]} …)
+
+            :.hover:bg-white
+        "#;
+
+        Clojure::test_extract_contains(input, vec!["flex", "first:lg:pr-6", "first:2xl:pl-6", "group-hover/2:2xs:pt-6", "hover:bg-white"]);
+    }
 }