New build process

[JimBobSquarePants]

Prerequisites

• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
• I have verified that I am following matches the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules 👮.
• I have provided test coverage for my change (where applicable)

Description

• Adopts Github Actions as a build process
• Updates dependencies
• Move targets to sensible values.
• Optimize no-command pipline

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@589086b). Click here to learn what that means.
The diff coverage is 85.71%.

@@            Coverage Diff            @@
##             master      #84   +/-   ##
=========================================
  Coverage          ?   75.68%           
=========================================
  Files             ?       47           
  Lines             ?     1316           
  Branches          ?      228           
=========================================
  Hits              ?      996           
  Misses            ?      256           
  Partials          ?       64

Flag	Coverage Δ
#unittests	75.68% <85.71%> (?)

Impacted Files	Coverage Δ
src/ImageSharp.Web/FormattedImage.cs	84.61% <ø> (ø)
...eSharp.Web/Providers/PhysicalFileSystemProvider.cs	84.21% <0%> (ø)
...s.Azure/Providers/AzureBlobStorageImageProvider.cs	76.47% <100%> (ø)
.../ImageSharp.Web/Middleware/ImageSharpMiddleware.cs	73.46% <91.66%> (ø)

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[tocsoft]

lgtm 👍