Add net462 targeting #308

Job	Run time
Code Coverage	3m 15s
Test (ubuntu, net6.0)	1m 0s
Build (ubuntu-latest, netstandard2.0)	15s
Test (macos, net6.0)	1m 4s
Build (ubuntu-latest, netstandard2.1)	21s
Build (ubuntu-latest, net6.0)	27s
Build (ubuntu-latest, net462)	18s
Build (windows-latest, netstandard2.0)	1m 35s
Build (windows-latest, netstandard2.1)	1m 42s
Build (windows-latest, net6.0)	1m 47s
Build (windows-latest, net462)	1m 44s
Build (macos-latest, netstandard2.0)	20s
Build (macos-latest, netstandard2.1)	18s
Build (macos-latest, net6.0)	21s
Build (macos-latest, net462)	25s
Pack	1m 50s
	16m 42s

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