feat: support custom parsers

[43081j]

Adds support for custom parsers in the --parser option.

This wasn't previously supported since the option is defined with a hard coded enum of the default parsers.

cc @fabiospampinato

Blocked until tiny-bin supports overriding options

[fabiospampinato]

Awesome, thanks! I'll do the wiring with the override option thing 👍

[fabiospampinato]

There are a few details I hadn't considered regarding overriding options 🤔 --color and --no-color are essentially the same flag, but kinda? what if one just wants to document both of them in the help page? Also one may not necessarily want to preserve the position of the overridden option, for example if one is overriding a default option 🤔 I need to fix these once I get to a place with a reasonable wifi connection.