contributing docs: add instructions for economically restarting failed CI jobs, debugging failed CI (#15576)
contributing docs: add instructions for economically restarting failed CI jobs, debugging failed CI (#15576)

* contributing docs: add instructions for economically restarting failed CI jobs, debugging failed CI

* fixup
dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim