[NEW CHECK] check dependabot

[mcm1957]

I'm sure that

• This issue does not report a false-positive detection (use dedicated template for this)
• This issue does not request a change or removal of existing check (use dedicated template for this)
• There is no other (open) issue with the same topic (use the search!)

Description of check to be added

If dependabot is set up (and only if it set up !) check

that package.json / npm is part of setup (-> error)
that github is part of setup (-> error)
that randomization is active (-> warning)
that open pull request limit is 15 oder higher
open pull request limit 10 - 15 -> suggestion
open pull request limit 5 - 10 -> warning
open pull request limit < 5 -> error

Link to repository

n/a

Checker version

5.1.0

[mcm1957]

5.4.0