Improve documentation

[LostXOR]

This PR makes a few small improvements to the docs:

• Changes "Download referenced assets" to the correct "Download assets"
• Changes the description in the plain text format section to not say it's the best for archiving (file sizes of both plain text and JSON are very small, and JSON has far more data)
• Changes the GUI instructions to be cross-platform
• Makes the formatting in the GUI settings list consistent and fixed a note being in the wrong spot
• Makes the CLI instructions for changing directories clearer

[Tyrrrz]

Thanks!