fix(id-class-value): fix inefficient regex

The positive lookahead assertion `(?= ...)` is used to ensure that the check occurs after the first
lowercase letter and all subsequent characters have been verified to resolve the issue of reference
backtracking

htmlhint#1147

src/core/rules/id-class-value.ts

@@ -17,7 +17,7 @@ export default {
  'The id and class attribute values must be in lowercase and split by a dash.',
  },
  hump: {
- regId: /^[a-z][a-zA-Z\d]*(?:[A-Z][a-zA-Z\d]*)*$/,
+ regId: /^[a-z](?=[a-zA-Z\d]*$)(?:[a-zA-Z\d]*(?:[A-Z][a-zA-Z\d]*)*)?$/,
  message:
  'The id and class attribute values must meet the camelCase style.',
  },