enable dependabot for GitHub actions

[ranocha]

This allows to get updates for GitHub actions automatically. I have used this for my own packages, the Trixi.jl framework, and the SciML organization. After merging this, you could also enable other Dependabot actions in 'Settings -> Code security and analysis -> Dependabot alerts' and '... -> Dependabot security updates'.

See https://github.com/SciML/MuladdMacro.jl/pull/37

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: +2.58 :tada:

Comparison is base (a9cee10) 47.52% compared to head (8337952) 50.11%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #33      +/-   ##
==========================================
+ Coverage   47.52%   50.11%   +2.58%     
==========================================
  Files          13       13              
  Lines         425      447      +22     
==========================================
+ Hits          202      224      +22     
  Misses        223      223              

see 8 files with indirect coverage changes

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.