Migrate documentation from Wiki to Read The Docs

[ederjc]

Migrate documentation from Wiki to Read The Docs

Changes from previous PRs:

• https://github.com/Infineon/XMC-for-Arduino/pull/299
• https://github.com/Infineon/XMC-for-Arduino/pull/300
• https://github.com/Infineon/XMC-for-Arduino/pull/301
• https://github.com/Infineon/XMC-for-Arduino/pull/302
• https://github.com/Infineon/XMC-for-Arduino/pull/303

New changes:

• Update CONTRIBUTING.md
• Remove all Wiki content & replace links by RTD

Rendered preview:

https://xmc-arduino-staging.readthedocs.io/en/latest/index.html

PR Edits

• Rebased to remove redundant commit messages.
• Merged master into this branch to resolve merge conflicts

[ederjc]

Happy to finally get this moved to RTD 👍 A few small topics.

Only the platform.txt and tools/xmc-flasher.py script. Be sure that is well synched, and not overwriting a latest version of these files. No need to make a separate PR for me (even that would be the ideal), but be sure the changes are relevant.

There were actually no changes on these files, but the rebase somehow brought them up. I merged the master into this branch and now it should be fine.