Texlite

- Fixed parsing of unnumbered sections (e.g. `* Section`).

- Fixed bug with using `---` as em-dashes causing errors.

- Decreased distribution build size by removing unneeded files from `MANIFEST.in`.
- Simplified the `--help` output.
- Updated README with more details on usage.
- Tweaked `--default-packages `F to append to (instead of overwrite) default packages, to prevent dependency issues.
- Improved output messages.

- Added link to repo in command-line `--help` for more information.
- Greatly improved codebase readability and internal documentation for future development.
- Cleaned up documentation.

- Solved critical config issue with reading in default packages.

- Cleaned up some capitalisation inconsistency.
- Decreased distribution build size by excluding some unnecessary files.