Implementation of the module for the sensor "SGP30"

[vrubel]

I'm not sure if your policy allows to create submodules. Please look at the proposed changes. If the existence of submodules is unacceptable, I will be ready to suggest an option with copies of files from the vendor's repository.

[loboris]

Thank you for the PR.

I would propose to make the MicroWebSrv related PRs directly to the original repository.

I'll look at the proposed SGP30 module. Generally, there are so many I2C sensors that it would be impossible to make the drivers/modules for all of them. Maybe it would be more useful and interesting to create the driver/module in Python, that way the users can learn something analizyng the code (and modify it if necessary) and the performance is usually more tha enough for most I2C devices.