docs: fix sphinx build errors, broken links, and typos

[ayan-waqas]

Summary of Changes

This PR resolves several documentation errors, Sphinx build warnings/errors, and broken links across the codebase:

• Sphinx Build Errors:

  • Removed an orphan empty .. note:: directive at the end of docs/installing/guided.rst.
  • Updated autofunction to autoclass with the full module path archinstall.lib.installer.Installer in docs/archinstall/Installer.rst.
  • Added Configuration toctree in docs/index.rst to fix unreferenced document warnings (disk_config, disk_encryption, custom_commands).
  • Added autodoc_mock_imports = ['parted'] in docs/conf.py for C-extension compatibility.

• Links & Examples:

  • Fixed link target for interactive_installation.py and replaced #docs-todo anchor in README.md.
  • Fixed PyPI link target schema (https://) in docs/installing/python.rst.
  • Corrected malformed RST code block markup and added missing --script flag in docs/examples/python.rst.
  • Removed invalid trailing commas in JSON object keys in docs/cli_parameters/config/disk_config.rst.

• Grammar & Typos:

  • Fixed "It's limitation" -> "Its limitation" and "scarse" -> "scarce" in docs/archinstall/plugins.rst.
  • Fixed "Or you can PyPa's" -> "Or you can use PyPA's" in docs/installing/python.rst.

Verification

Ran sphinx-build -b html -W docs/ docs/_build (warnings treated as errors); build succeeded with 0 warnings and 0 errors.