Use bon for an infallible and compile-time-checked builder

[Veetaha]

Hi! This PR replaces the usage of derive_builder with bon. What does it give us?

• The build() method no longer returns a Result<T>, it returns T instead. So there are no potential panics and no need for error handling in runtime. For example:
  
• The builder generated by bon validates that the same field isn't set twice. For example, with bon I detected this mistake in tests where math_dollars and math_code were set twice, because bon generated a compile error

  comrak/src/tests/api.rs

  Lines 62 to 67 in 1a33c63

  	extension.math_dollars(false);
  	extension.math_code(false);
  	extension.front_matter_delimiter(None);
  	extension.multiline_block_quotes(false);
  	extension.math_dollars(false);
  	extension.math_code(false);

• bon generates a T::builder() method, which removes the need for importing the TBuilder type and using TBuilder::default() syntax to create the builder.
• If you ever need some more complex logic of building, or you want to avoid create a separate "parameters" struct, you can always generate a builder from a function or from a method with bon. Builders generated this way use the same API conventions and it is even possible to switch between struct/function syntax and keep your crate API the same (see e.g. switching from #[derive(Builder)] to a #[builder] on the method named "new")

I understand this is a breaking change for this crate, but I think improvements are worth it.

[Veetaha]

For optional fields (or fields with #[builder(default)]) bon generates two setters:

• <field>(value: T)
• maybe_<field>(value: Option<T>)

This is desingned this way so that changing a required field to optional is compatible, and it also simplifies the syntax for optional members by removing the need to wrap the value with Some() using the <field> setter like here, for example:

[Veetaha]

UPD: bon 2.2.1 added support for MSRV 1.59.0

[kivikakk]

Thanks so much for all the effort you put into this! This is amazing, it looks really nice, thank you!

I'll rebase it and get it passing CI. :)

[kivikakk]

Thank you again! 🤍