Revisit `Markd::Options` class

[devnote-dev]

I think that there could be some changes/improvements to the current Options class:

• Removing unimplemented options: given that they're not used, there's no actual reason to have them in the class – having a TODO comment or similar in place would be better for whomever wants to implement them
• Removing time: I understand the purpose but this is really something that users could implement themselves if they wanted that information, and it's relatively easy to do
• Replace safe: I like this option, but it is quite restricting – if you wanted to allow table HTML and nothing else, there would be no way to do that without performing string manipulation post-rendering. I think it would be better to change this into something like sanitize which gives you options on what HTML elements you want to allow, there is a sanitize shard that would be great for this
• Rename prettyprint: (this one isn't important, but pretty_print makes so much more sense here lol)

WDYT?