add git rebase step-by-step guide in "standards for merging and branching" page

[avallecam]

Is your feature request related to a problem? Please describe.
For tutorial contributors, I consume and redirect others to steps on how to rebase

Describe the solution you'd like
Redirect from the CONTRIBUTING file to the blueprints for this step-by-step guideline after the committing branches comic.

Additional context
An alternative I thought was also to redirect to a git-training discussion entry but would be without context.

[chartgerink]

@avallecam is my understanding correct that this issue is related to blueprints, not the website itself?

[avallecam]

@avallecam is my understanding correct that this issue is related to blueprints, not the website itself?

transferred :)