Docs: large update to the concepts/ section

[zilto]

Multiple pages were updated from the docs concepts/ section.

Changes

• pages added
• content from blogs, examples, API references was integrated into Concepts pages
• lexicon renamed to glossary
• fixed a few random files that had outdated / incorrect code examples

How I tested this

• ran pre-commit hooks
• built documentation locally

Notes

• ❗ would be beneficial to sprinkle links to tryhamilton.dev where relevant
• ❗ there are a few #TODO left in the body of the text
• would need a second pair of eyes to review the docs from the browser

[skrawcz]

@zilto had to rebase to resolve conflict -- otherwise looks good. Do a squash merge and add a nice commit message.