Deprecate delegated check_* methods

[snacks02]

I noticed these weren't private when playing with CrystalDoc.info.

This is indeed a breaking change, so the next release will have to be 2.0.0.

[Vici37]

Looks good to me!

This is a rather unremarkable reason to update a major version, though. As an alternative, what if instead we marked the methods with:

# :nodoc:
@[Deprecated("The visibility of this method will be changing in the future, and it should not be used directly")]
delegate check_jpeg, to: self.class

And then during a more noteworthy major release change, go through and clean up any @[Deprecated] methods that were identified? That way we avoid the trap of doing a major version update for every technically-breaks-backwards-compatibility bug fix 😅

What do you think?

[snacks02]

Apparently it doesn't work in the suggested order, but does work reversed.

require "./src/pluto"
require "./src/pluto/format/webp"

class Test
  include Pluto::Format::WebP
end

Test.new.check_webp(1)

> crystal test.cr
In test.cr:8:10

 8 | Test.new.check_webp(1)
              ^---------
Warning: Deprecated Test#check_webp. The visibility of this method will be changing in the future, and it should not be used directly

A total of 1 warnings were found.

[snacks02]

Awesome suggestion, btw!

[Vici37]

🚀