Shorten contribution section in ReadMe and make it more friendly

[bergmeister]

PR Summary

I find that the current contribution section is too lengthy, seems to rather scare off people and just repeats commonly known best practices that are not specific to this repo.

PR Checklist

Note: Tick the boxes below that apply to this pull request by putting an x between the square brackets. Please mark anything not applicable to this PR NA.

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• [NA] User facing documentation needed
• Change is not breaking
• [NA] Make sure you've added a new test if existing tests do not effectively test the code changed
• This PR is ready to merge and is not work in progress
  • If the PR is work in progress, please add the prefix WIP: to the beginning of the title and remove the prefix when the PR is ready

[JamesWTruher]

very nice