Added
- `parseLatex`. Developing this feature - parsing a LaTeX string for editing by MathKeyboardEngine - started after a [question thread](https://github.com/orgs/MathKeyboardEngine/discussions/1) was opened by [chengyi](https://github.com/WCY91).
- `insert` previously only accepted a single `TreeNode`, but it can now handle a `TreeNode[]` too.