Replace `JN` with `JD` text and `StratumV2` with `Stratum v2`

[pavlenex]

It doesn't do any contextual edits. We'll have to do some work on docs/index.md in general as it doesn't seem accurate in general. @GitGab19 maybe this edits of /docs/index.md is something you'd like to review in the future, but for now this PR specifically addresses #175 text, image replacement will follow in another PR as I edit out the graphics.

closes #175

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[GitGab19]

It doesn't do any contextual edits. We'll have to do some work on docs/index.md in general as it doesn't seem accurate in general. @GitGab19 maybe this edits of /docs/index.md is something you'd like to review in the future, but for now this PR specifically addresses #175 text, image replacement will follow in another PR as I edit out the graphics.

closes #175

Agree with you. There is something to change there. Next week I think I'll get time to have a general review and propose some changes!

[pavlenex]

Thanks for a review @GitGab19 Addressed all your suggestions in https://github.com/stratum-mining/stratumprotocol.org/pull/182/commits/82a443ac23604eb511c76f8b8a20b2d14494bd04

There are probably a lot of things we'd have to do in GettingStarted.md as it still has a lot of mentions on JN, but let's do that in a separate PR where we will focus on simplifying docs and ensuring it's correct with our latest changes.

[pavlenex]

@GitGab19 I've reverted the docs/index.md page since you're working on it in #187 so I think we can merge this one.