Plotsquared/reworking

[RedstoneFuture]

Overview

Reworking of some PlotSquared docu pages

Fixing #44

Description

• Reworking README, adding cover picture
• Removing .yml from the page name of the setting docs
• Small markdown typo
• Fixing links
• Updating infos
• Renaming "Changelog v4 & v5" page
• Updating "Why PlotSquared" page
• Some typos

EDIT (06.01.2023)

• Removing commands already removed from plugin
• Updating source-code link to main branche

### Submitter Checklist
- [X] Make sure you are opening from a topic branch (**/feature/fix/docs/ branch** (right side)) and not your main branch.
- [X] Ensure that the pull request title represents the desired changelog entry.
- [X] New public fields and methods are annotated with `@since TODO`.
- [X] I read and followed the [contribution guidelines](https://github.com/IntellectualSites/.github/blob/main/CONTRIBUTING.md).

[RedstoneFuture]

Can this be merged? I am already reworking the FAWE articles.

[NotMyFault]

friendly ping @IntellectualSites/plotsquared-team :)