Semver compat

Author: kornelski

.github/workflows/ci.yml

@@ -47,7 +47,12 @@ jobs:
         run: cargo clippy --all-targets --manifest-path=c-api/Cargo.toml --target-dir=target
       - name: Run clippy on JS API
         run: cargo clippy --all-targets --manifest-path=js-api/Cargo.toml --target-dir=target
-
+    - name: Check semver
+      uses: obi1kenobi/cargo-semver-checks-action@v2
+      with:
+        package: lol_html
+        feature-group: default-features
+        verbose: true
   test:
     name: Test
     runs-on: ubuntu-latest

src/selectors_vm/error.rs

@@ -45,6 +45,11 @@ pub enum SelectorError {
     #[error("Invalid or unescaped class name in selector.")]
     InvalidClassName,
 
+    /// Unused
+    #[error("Empty negation in selector.")]
+    #[deprecated(note = "unused")]
+    EmptyNegation,
+
     /// Unsupported combinator in the selector.
     #[error("Unsupported combinator `{0}` in selector.")]
     UnsupportedCombinator(char),