readme TOCs + formatting

(intro: i've never contributed to open source before but want to get involved - dwyl looks like a great place to get started. hi!)

quite a lot of the dwyl readmes are really daunting to look at. and i feel it would be good to add a table of contents to the top of each one, so you can immediately see what you're about to read and jump to parts that interest you, or to make things easier to find later on, or to make it easier to see if a readme is missing any sections.

in terms of formatting, they could make use of horizontal rules to separate sections of text. there's also an insane overuse of italics, but that might just be my personal opinion...

as a first contribution, i'm willing to go through some repos (starting with this one) and tidy up the readmes (making sure not to change any of the content).

let me know if you think this is worthwhile + feel free to add any other suggestions. ✌🏻