Add tutorial: Build a JSON Parser (Python)

[shaongitbd]

Adds Build a JSON Parser under Python.

It's a free, interactive course where you build a JSON parser from scratch — tokenizer, recursive-descent value parser, full string-escape handling including \uXXXX surrogate pairs, and the strict number grammar — running your code against tests as you go.

There's no JSON parser tutorial in the list yet, so this fills a gap. Placed under Python and formatted per CONTRIBUTING.md.

[tuvtran]

Thanks for the suggestion. A JSON parser tutorial would genuinely fill a gap here, but this link points to a course landing page that requires signing up on a commercial platform before any content is visible, and this list only accepts tutorials that are freely and openly readable. If you know of an open-access JSON parser walkthrough, we'd be happy to see a new PR.

[shaongitbd]

Thanks for the review, and I appreciate it!

Quick clarification on the platform, since I think there's a misunderstanding: shipthatcode courses are open to guests — no signup or login is required to read and work through the full content. The "Get started free" button is an optional account (just for saving progress); open any lesson directly and the whole tutorial loads immediately as a guest, with no account and no paywall/freemium gate.

For this JSON-parser course, the complete build is freely readable without an account — the tokenizer, the recursive-descent value parser, full string-escape handling including \uXXXX surrogate pairs, and the strict number grammar.

I'm glad to share a direct lesson link so you can confirm there's no login wall. On that basis I believe it meets the "freely and openly accessible" criterion — would you reconsider?

Thanks for maintaining the list!