Move all external images to within the repo

[akleemans]

Move all images from external sources to this repository.

Solves the following issue: #158

Some notes:

• As discussed in the issue above (and noted in the contribution guidelines), image links to retroachievements.org are also considered external and are added to this repository.
• Links from camo.githubusercontent.com were not accessible directly anymore, so I used the images provided by archive.org (Example)
• Some images on translated pages have been updated to the newest in the English version. Examples: memsizes.png => mem-inspector-size-diagram.png, images on memory-inspector.md (memoryinspector-num.png, memoryinspector-filter.png, memoryinspector-bookmark.png etc.)
• Badge image names have been kept according to the RA site ID.
• The devquest images have been numbered accordingly to the devquest ID.
• Image names are now all consistently using a dash (-), some underscores (_) were replaced.
• I added an alt text to the images where missing, and tried to replace generic ![image](...) descriptions with something more meaningful. I did not fix all existing alt texts, they are not all aligned currently, but I focussed on the image replacements.
• I didn't replace the labels in docs/guidelines/content/hash-labels.md (yet) - I was hesitant if those should be duplicated to this repo, as they are referenced directly (and used as image tags) from all the "Supported Game Files" pages. If they should also be included here please let me know. (I did update the image links in the pt version, there was an update to the image links in the English version which was not applied in pt).
• If there were more than to 5-10 images for a single topic, I tried to prefix the images, like rabot-*.png for the Discord RA Bot page. If I get it correctly a flat directory structure of public is desirable, so I didn't create subfolders.
• Checked for duplicate images using image checksums

❓Question: When running the docs locally, I got warnings:

Files in the public directory are served at the root path.
Instead of /public/badge-64969.png, use /badge-64969.png.

But the contributing-to-the-docs.html explicitly states to use image links with the /public prefix:

✅ GOOD
...(/public/current-branch.png)

Can the local warnings be ignored?

[wescopeland]

When running the docs locally, I got warnings

Good question. It's possible VitePress changed something in a recent update.

I think we should probably:

• Respect the warning and update the paths.
• Update our own contributing docs to correct the error you've pointed out.