HMAC-SHA256 support

[ehsan310]

I would like to ask you whether you have a plan to add HMAC-SHA256 algorithm ?
SHA1 is deprecated in many application and i need sha256 to sent to my backend.

[agentzh]

@ehsan310 We can make that configurable in this module. But we should still keep SHA1 for backward compatibility. Will you create a pull request for it please? Thanks!

[erankor]

Opened #57, thanks!

[rpoitras]

@agentzh Would love to see this go in. 🙏