More resilient conversions from strings

[pashadia]

• Added case-insensitive conversions, so that e.g. Card::from("AH") works
• Added clearer error messages when the conversion fails

[Nydauron]

Thanks for the PR! This looks good for the most part.

Could you add some documentation to Suit::from_char explaining that the character is case-insensitive?

Also, CI failed to run due to clippy failing (assumably because some clippy rule was updated). I already went ahead and reordered the CI steps and fixed the clippy error on master. As I was writing this, I saw you made a push fixing it on this feature branch, and while I appreciate the change, I'd suggest popping off that commit and making that a separate PR.

[pashadia]

Hey!

I've removed the CI-related commit, and I've added the documentation to the Suit::from_char() function.

As I've done that, I see that I've done the case-insensitive implementation for the Value conversion in the impl TryFrom<char> for Value block, instead of inside Value::from_char(). Functionally, it's the same thing, but I think these should have similar implementations -- would you like me to change the Value impl so that it's similar to the Suit ?

[pashadia]

Rewritten the Value conversion from char in a similar fashion to Suit. Let me know if you have any comments.

[Nydauron]

LGTM, thanks!