Convert readme to markdown

[casey]

Now that GitHub auto-generates a table of contents, I think asciidoc has outlived its usefulness, and I should convert the readme to markdown so I don't have to remember the asciidoc syntax.

[kenden]

Now that GitHub auto-generates a table of contents

@casey Now that the README.md is in markdown, is the table of contents coming back? I find it helpful to navigate the docs and don't see it anymore, am I missing it?

[casey]

GitHub actually automatically generates a table of contents now, but it can be hard to find. There's a button that opens a drop-down menu, which has a search bar to search for individual sections.

[casey]

(It's the icon to the left of README.md.)

[kenden]

@casey thank you!
I just saw a README.me with the text:
Feeling lost? Use the GitHub TOC!), here: https://github.com/nanotee/nvim-lua-guide

Do you think this would be a good idea to add this here too?

[casey]

Sounds reasonable to me, I just opened #1096 to add an arrow pointing to the table of contents.