Generalize markdown driven page component

"Install OCaml" demonstrates a markdown driven page. Generalize it's implementation, attempting to deal with all of the following issues:

• Use a generic page component which renders all markdown files within a given directory (or directory subtree, if preferred). getStaticPaths should help in implementing this
• Consider how the markdown file names will map to urls
• Initially use a tag for all links
• Refactor link generation to use NextJS Link component for internal links or accept limitations of not using NextJS Link component in this situation.
• Improve general text and code block styling. Do not address highlighting in this issue. Highlighting will be dealt with in Implement code highlighting #137.

Note: Create a follow-up issue to design and implement the mobile rendering of the table of contents.

• Use a generic page component which renders all markdown files within a given directory (or directory subtree, if preferred). getStaticPaths should help in implementing this
• Consider how the markdown file names will map to urls
• Initially use a tag for all links

These were all done in #252

Refactor link generation to use NextJS Link component for internal links or accept limitations of not using NextJS Link component in this situation.

As part of #296 , I chose to use rehype-stringify, which does not allow for React elements. Since we cannot use React elements, I have chosen to accept the limitations of not using NextJS Link component in the body of rendered markdown.

[agarwal]

@Kanishka-work Consider closing this and making followup issues for design improvements.

Improve general text and code block styling. Do not address highlighting in this issue. Highlighting will be dealt with in #137.

We'll create a follow-up issue for this.