detect all variables that start with --

This was already the case before, but we were also verifying that it was
preceded by `var(`. Let's remove that code to make sure code like this
works:
```js
let var = '--my-var';
let style = bla.getPropertyValue(var);
```

crates/oxide/src/parser.rs

@@ -159,7 +159,7 @@ impl<'a> Extractor<'a> {
         }
 
         while !candidate.is_empty() {
-            match Extractor::is_valid_candidate_string(candidate, self.input, self.idx_start) {
+            match Extractor::is_valid_candidate_string(candidate) {
                 ValidationResult::Valid => return ParseAction::SingleCandidate(candidate),
                 ValidationResult::Restart => return ParseAction::RestartAt(self.idx_start + 1),
                 _ => {}
@@ -240,11 +240,7 @@ impl<'a> Extractor<'a> {
     }
 
     #[inline(always)]
-    fn is_valid_candidate_string(
-        candidate: &'a [u8],
-        input: &[u8],
-        start_idx: usize,
-    ) -> ValidationResult {
+    fn is_valid_candidate_string(candidate: &'a [u8]) -> ValidationResult {
         // Reject candidates that start with a capital letter
         if candidate[0].is_ascii_uppercase() {
             return ValidationResult::Invalid;
@@ -307,14 +303,6 @@ impl<'a> Extractor<'a> {
             }
         }
 
-        // CSS variables must be preceded by `var(` to be considered a valid CSS variable candidate
-        if candidate.starts_with(b"--") {
-            match input.get(start_idx - 4..start_idx) {
-                Some(b"var(") => return ValidationResult::Valid,
-                _ => return ValidationResult::Invalid,
-            }
-        }
-
         let split_candidate = Extractor::split_candidate(candidate);
 
         let mut offset = 0;
@@ -1738,44 +1726,31 @@ mod test {
         );
     }
 
-    #[test]
-    fn test_css_variables_must_be_preceded_by_var_open_paren() {
-        let candidates = run("[--do-not-emit:true]", false);
-        assert_eq!(
-            candidates,
-            // Looks little funky, but `--do-not-emit` on its own is not emitted
-            vec!["[--do-not-emit:true]", "--do-not-emit:true"]
-        );
-
-        let candidates = run("<div style={{ '--do-not-emit': true }}>", false);
-        assert_eq!(candidates, vec!["div", "style", "true"]);
-    }
-
     #[test]
     fn test_is_valid_candidate_string() {
         assert_eq!(
-            Extractor::is_valid_candidate_string(b"foo", b"", 0),
+            Extractor::is_valid_candidate_string(b"foo"),
             ValidationResult::Valid
         );
         assert_eq!(
-            Extractor::is_valid_candidate_string(b"foo-(--color-red-500)", b"", 0),
+            Extractor::is_valid_candidate_string(b"foo-(--color-red-500)"),
             ValidationResult::Valid
         );
         assert_eq!(
-            Extractor::is_valid_candidate_string(b"bg-[url(foo)]", b"", 0),
+            Extractor::is_valid_candidate_string(b"bg-[url(foo)]"),
             ValidationResult::Valid
         );
         assert_eq!(
-            Extractor::is_valid_candidate_string(b"group-foo/(--bar)", b"", 0),
+            Extractor::is_valid_candidate_string(b"group-foo/(--bar)"),
             ValidationResult::Valid
         );
 
         assert_eq!(
-            Extractor::is_valid_candidate_string(b"foo(\"bg-red-500\")", b"", 0),
+            Extractor::is_valid_candidate_string(b"foo(\"bg-red-500\")"),
             ValidationResult::Restart
         );
         assert_eq!(
-            Extractor::is_valid_candidate_string(b"foo-(", b"", 0),
+            Extractor::is_valid_candidate_string(b"foo-("),
             ValidationResult::Restart
         );
     }