docs: improve development documentation

[christian-bromann]

Pull request checklist

Please check if your PR fulfills the following requirements:

• [x] Tests for the changes have been added (for bug fixes / features)
• [x] Docs have been reviewed and added / updated if needed (for bug fixes / features)
• [x] Build (npm run build) was run locally for affected output targets
• [x] Tests (npm test) were run locally and passed
• [x] Prettier (npm run prettier) was run locally and passed

Pull request type

Please check the type of change your PR introduces:

• [ ] Bugfix
• [ ] Feature
• [x] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [x] Documentation content changes
• [ ] Other (please describe):

What is the current behavior?

With the recent changes to Vue and React output targets some things have changed that haven't been documented. This patch updates the development docs of this project.

What is the new behavior?

• consolidate development commands, e.g. dev, test.watch, test.unit
• document development commands
• add more code documentations
• fix type issues with Vue SSR implementation

Does this introduce a breaking change?

• [ ] Yes
• [x] No

Other information