Get from extension

[ririsoft]

This PR adds some get_from_* utilities I have been missing from Infer: checking the extension corresponding to a given mime type string and getting the mime type from a file extension without file system access.

[ririsoft]

I will rebase once #17 is merged

[paolobarbolini]

Looks good to me

[bojand]

👍
I'll let you and @paolobarbolini run with the PRs and changes.
I am pretty swamped today and most of the weekend (but have access to internet + computer); I have added @paolobarbolini as a collaborator so he should be able to merge and tag.
Please make sure to update the crate version in Cargo.toml before tagging a release.
To do a release once everything is ready just tag the release and push the tag, the GitHub actions should handle the rest. Sometimes the git-chglog portion doesn't seem to generate the changelog (no commits) within the action but you can manually create release notes if there are issues.
Feel free to tag me in an issue and I can respond / unblock as promptly as possible.
Thanks for all the changes this is super cool!