Various tweaks

[sebromero]

This PR contains various fixes and small enhancements:

• Fix incorrect file extension in package file: Template file was not included correctly in package file
• Remove unused variables: Unused variables in runtime file were removed
• Remove test code: Test code in runtime is better added to a file that is not part of the runtime itself
• Add additional documentation: Improve documentation in the code
• Add type hints: Added type hints to functions from runtime
• Move meta data to init file: Meta data should live in the init file
• Clarify various points in readme file: Read through the readme and addressed some unclarities.
• Avoid platform specific duty cycles: Changed analog_write function to use non-platform specific API.
• Make version consistent: Version in init and package file were different.

[ubidefeo]

great contribution
LGTM