build: Add encrypted strong name signing key file
build: Add encrypted strong name signing key file

Using secure-file tool, installed via nuget.
Will be decrypted by build server and passed
to build.bat.

The PFX file is also password protected and must
be installed on the build agent in order to
sign during build.

BrandonLWhite/UnitsNet,anjdreas/UnitsNet,anjdreas/UnitsNet,BrandonLWhite/UnitsNet