Add JSDoc comments to various utility functions and core files.

This change adds JSDoc-style comments to several functions and classes across the codebase to improve readability and maintainability.

Comments were added to:
- `src/SEQTA.ts`: Explained the `init()` function.
- `src/seqta/utils/waitForElm.ts`: Detailed the `waitForElm()` function, its parameters, and behavior.
- `src/seqta/utils/stringToHTML.ts`: Clarified the `stringToHTML()` function, including its sanitization and styling features.
- `src/seqta/utils/delay.ts`: Added a brief explanation for the `delay()` utility.
- `src/seqta/utils/mutex.ts`: Documented the `Mutex` class and its `acquire` method (renamed from `lock`), explaining its asynchronous locking mechanism and the role of the returned unlock function.

src/seqta/utils/delay.ts

@@ -1,3 +1,12 @@
+/**
+ * Pauses execution for a specified number of milliseconds.
+ *
+ * This function returns a Promise that resolves after the given delay,
+ * allowing it to be used with `async/await` to pause asynchronous operations.
+ *
+ * @param {number} ms The number of milliseconds to delay.
+ * @returns {Promise<void>} A Promise that resolves after the specified delay.
+ */
 export function delay(ms: number) {
   return new Promise((resolve) => setTimeout(resolve, ms));
 }