First attempt at adding support for the RMT device.

[pjsg]

Fixes #3492.

• [x] This PR is for the dev branch rather than for the release branch.
• [x] This PR is compliant with the other contributing guidelines as well (if not, please describe why).
• [ ] I have thoroughly tested my contribution.
• [x] The code changes are reflected in the documentation at docs/*.

This is a new component that allows the sending and receiving of arbitrary pulse sequences using the rmt device on the ESP32 parts. It was designed for driving remote control protocols.