Update README to use status badge table, rephrase reference to MTEX

[hakonanes]

Description of the change

The current README.rst have started to show underscores after badges. Should be fine now.

1. Given how much this project has moved on from its beginning, I've rephrased the reference to MTEX in the README from

[...] heavily inspired by the MATLAB package MTEX.

to

Initiation of the package was inspired by MTEX.

2. I've organized badges in a table similar to how we do it in kikuchipy, which was inspired by PyVista.

3. And, I've changed the phrasing under "Citing orix" slightly to more strongly encourage citation of both the 2020 paper and the software (Zenodo DOI).

Progress of the PR

• [n/a] Docstrings for all functions
• [n/a] Unit tests with pytest for all lines
• [n/a] Clean code style by running black via pre-commit

For reviewers

• The PR title is short, concise, and will make sense 1 year later.
• New functions are imported in corresponding __init__.py.
• New features, API changes, and deprecations are mentioned in the unreleased
  section in CHANGELOG.rst.
• Contributor(s) are listed correctly in __credits__ in orix/__init__.py and in
  .zenodo.json.

[harripj]

Thanks for fixing the underscores, nice spot! I'm happy with all the changes here.