Submit open-mastr paper to joss

[FlorianK13]

For a paper submission, we need to do the following:

• [x] Create a branch containing a paper.md file
• [x] Release v0.14.0
• [x] Update the documentation to mkdocs
• [x] Conduct an own review of open-mastr, following the checklist described here
• [x] Run the whole paper.md file through a spell checker
• [x] Get permission from all authors to submit paper

Tasks within the paper

• [x] Add orcids of all authors
• [x] Add affiliation of all authors

[FlorianK13]

Paper is submitted - search for editors and reviewers has started, see https://github.com/openjournals/joss-reviews/issues/6199#issuecomment-1884016695