Add support of PlatformIO

[KingOfGerrit]

Please, add support of PlatformIO.
All files that needed prepared.

[martinmoene]

Thanks for your contribution.

Before I continue, I'd like to inform myself a little on PlatformIO.

Two suggestions right away:

1. Add the license to the library.json file: "license": "BSL-1.0",.
2. Add a terminating newline to both files.

[martinmoene]

PlatformIO, Creating Library reads:

PlatformIO has a built-in Library Management where developers can declare project dependencies and PlatformIO will automatically manage them (install, build, update). It doesn’t have any requirements for a library source code structure. The only requirement is a library manifest file - library.json, library.properties, or module.json. It must be located in the root of a library.

We highly recommend using library.json for better compatibility and avoiding any issues.

Thus I'm inclined to think it is perhaps not such a good idea to also include library.properties. See also Library.json or library.properties, which one takes precedence. It is however verywell possible that I'm not aware of its importance otherwise.

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Notes to self:

• The version number in library.json (and library.properties) must be updated by script/update-version.py.
• See Configuration, library.json in the PlatformIO documentation.
• Check for more keywords to add, other entries.
• The library must be published to the PlatformIO Registry using pio package publish command. Every time when you modify a source code of a library you will need to increment the “version” field in library.json manifest and re-publish again.

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Arduino IDE seems to uses library.properties, see e.g. Making your libraries available to Arduino IDE users by Steve Kemp.

[martinmoene]

Publishing to the PlatformIO Registry using the pio package publish command:

• In VSCode, open PlatformIO .
• Open terminal via Miscellaneous > PlatformIOCore CLI.
• Open PlatformIO local webpage via command: pio home.
• On webpage, right-top click account icon.
• Click GitHub to login via GitHub authentication.
• In terminal, issue Ctrl+c to exit PlatformIO Home.
• In terminal, make sure, the proper default folder is selected (.../optional-lite)
• In terminal, issue pio package publish.