Add version tags

[hkunz]

The sjpeg repository currently does not provide version tags, which makes it difficult to pin a stable release for builds or package management.

[skal65535]

@jzern did we ever tagged the repo? can't remember

[jzern]

@jzern did we ever tagged the repo? can't remember

No. It seems like we should at least get a baseline tag in. I've been meaning to push some micro-optimizations and non-runtime cpu detected AVX2 code for far too long. Maybe we check the latest build against modern compilers and tag before I do that.

[skal65535]

@jzern, we could just get all the optim in, verify + clean-up and make a proper 1.0 tag with it. Either way is fine