Remove BakedFile#mime_type

[straight-shoota]

Closes #17

[straight-shoota]

MIME type resolution should not need to be implemented multiple times but in a generic, reusable way. That's why this shouldn't be included in this shard.

There is an issue to bring a MIME registry to Crystal's stdlib and I've been working on that, but it's not ready yet. There are some shards available with a MIME registry, they can be used to resolve the MIME type at runtime. Depending on a system command at compile time is not a great idea because this would mean you need a properly configured registry on the build system if you don't want to face MIME type issues at runtime. That's just impractical. Shelling out to use a system tool is also not optimal, this should also be handled inside crystal.

[schovi]

@straight-shoota
Thanks for an explanation. Can you add an example of working shard to readme? Or can we wait with this PR until it will be available directly in stdlib?

[straight-shoota]

Let's wait for crystal-lang/crystal#5765. Should hopefully go in the next release.

[straight-shoota]

The MIME registry was finally released in Crystal 0.27.1, so this PR can now be merged.

Instead of baked_file.mime_type, the mime type can now be queried as MIME.from_filename(baked_file.path).
See stdlib API docs for more details.

[schovi]

@straight-shoota awesome 👍