Release v0.18.0

[terrillmoore]

Update README, etc. See delta in #123 for details.

• [x] ~update VERSION.txt version to v0.18.0~
• [x] update library.properties version to 0.18.0
• [x] update CATENA_ARDUINO_PLATFORM_VERSION in CatenaBase: change here: https://github.com/mcci-catena/Catena-Arduino-Platform/blob/3af42bb7963d638b6dfbf544027284c5a640dc9c/src/CatenaBase.h#L58
• [x] update README.md version for badges (line 7)
• [x] update README.md release history (towards end).
• [x] generate pull request
• [x] merge into master.
• [x] tag and release.

[terrillmoore]

The changes for input command editing and fixing the Si1133 should be generally available.