i37: Port to GitHub Actions

[richfitz]

Once this is done, outstanding PRs can merge this in and they'll be easy to deal with:

• Windows: update to hiredis 1.0.0 #35 just goes straight in (the commits from that PR now cherry-picked here)
• I31: Updates for CRAN #32 should be easy too
• Addresses #27: Adds support for making SSL connections to redis via hiredis 1.0.0+ #36 is more work, and probably wants this PR expanded so that the SSL support is included

Closes #37

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@178c521). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             master       #38   +/-   ##
==========================================
  Coverage          ?   100.00%           
==========================================
  Files             ?        18           
  Lines             ?      1476           
  Branches          ?         0           
==========================================
  Hits              ?      1476           
  Misses            ?         0           
  Partials          ?         0           

Impacted Files	Coverage Δ
src/registration.c	100.00% <ø> (ø)

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[weshinsley]

Changes reviewed and tested locally on Windows.