feat: Add additional TeXArg types

[Sub6Resources]

Description

Adds additional arguments to TeXArg to allow for more advanced customization and features.

For example, using a combination of TeXArg.underscore_braces, TeXArg.caret_braces, and TeXArg.braces, a user could implement a keyboard button that allows the user to type an integral, summation, or product.

Or, using the new TeXArg.parentheses_lr, a user can add more visually appealing parentheses as an argument to a keyboard button.

Related issues & PRs

Fixes #38

Checklist

Remove If [...] items that do not apply to your PR.

• I have made myself familiar with the CaTeX
  contributing guide.
• I added a PR description.
• I linked all related issues and PRs I could find (no links if there are none).
• If this PR changes anything about the main math_keyboard or example package
  (also README etc.), I created an entry in CHANGELOG.md (## UPCOMING RELEASE if the change
  on its own is not worth an update).
• All required checks pass.

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