Allow numbers in variable names

src/lexer.rs

@@ -372,7 +372,7 @@ impl<'a> Lexer<'a> {
         self.pos.next_char();
         let mut name = String::with_capacity(99);
         while let Some(c) = self.buf.peek() {
-            if !c.is_alphabetic() && c != &'-' && c != &'_' {
+            if !c.is_alphanumeric() && c != &'-' && c != &'_' {
                 break;
             }
             let tok = self

tests/main.rs

@@ -95,6 +95,11 @@ mod test_variables {
         "$a: red; a {\n  color: #{#{$a}};\n}\n",
         "a {\n  color: red;\n}\n"
     );
+    test!(
+        numbers_in_variable,
+        "$var1: red; a {\n  color: $var1;\n}\n",
+        "a {\n  color: red;\n}\n"
+    );
 }
 
 #[cfg(test)]