lockup: add graphs with schedule with lockup_duration to the doc

[telezhnaya]

I previously added the doc about lockup with pictures
near/docs#691

We need to add one more picture with explanation of deprecated lockup_duration, it's important for the understanding of existing lockups.

[telezhnaya]

Note for myself: Jake Stutzman is the right person to beautify my childish painting when it will be ready 🙂

[bucanero]

Hello @telezhnaya , please keep in mind that the "Lockup" document has been moved to the Wiki:
https://wiki.near.org/getting-started/near-token/lockups

If you want, I can add a redirect so the deprecated URL here is forwarded to Wiki.

[telezhnaya]

@bucanero maybe it's better to remove the duplicate in this case? It's better to have the only version, and fix it as needed.

When/why do we decide that docs.near.org is deprecated? I am sorry, I missed the discussion about that.

This page on Wiki has some issues. I saw there were no pictures at all: now they appeared. We have problem with bullet lists: https://wiki.near.org/getting-started/near-token/lockups#lockup (each point should be on the new line)
I haven't checked it fully, but we definitely need to compare the contents before any movements.

[bucanero]

Sure, I can remove the duplicate here, and keep a redirect to the Wiki to avoid 404s.

When the wiki was launched, the team decided that docs.near.org should focus on Developers, and other content should go to the Wiki. See here: near/devrel#255
You can also ping @thisisjoshford and @ilblackdragon about the rationale behind the move.

If you see any formatting issue, it's probably a small parsing difference between Docusaurus and Gitbook. You can edit the source here: https://github.com/near/wiki/blob/master/getting-started/near-token/lockups.md

Btw, you can also request access to a GitBook account, so you can edit Wiki articles directly using the visual interface from gitbook.com.

[telezhnaya]

We are removing the files from docs here near/docs#886