Feat/getting started guide

[pbelmann]

This PR represents a rewrite of the Getting Started section.

• Quickstart and Getting Started can by followed without checking out the git repository
• Getting Started section explains not only how to run the Toolkit on a cloud-based cluster but also how to add an analysis and how to exchange a tool of a module.
• All Getting Started scripts are part of the Github Action tests.

PR review guidelines

Thank you for submitting this PR.

Before merge:

• A PR must be reviewed by one of the team members.

• Please check if anything in the documentation must be adjusted, or added (development-setup, production-setup, user-guide).

• PRs with new modules or workflow interfaces must include tests according to the developer guidelines.

• The new code is readable, well commented and should adhere to our developer guidelines.

• Before merging it must be checked if a squash of commits is required.

Config updates

If you update any of the config files in the default folder, please make sure to also update the clowm/nextflow_schema.json if necessary.