Add support for CCS811 Air Quality Sensor

[wbvreeuwijk]

Adds support for CCS811 sensor

Make sure all boxes are checked (add x inside the brackets) when you submit your contribution, remove this sentence before doing so.

• [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).
• [x] I have thoroughly tested my contribution.
• [x] The code changes are reflected in the documentation at docs/*.

<Needed support for CC811 Air quality sensor>

[wbvreeuwijk]

First attempt at adding hardware support to NodeMCU. Support for CCS811 Air quality sensor.

[wbvreeuwijk]

Please consider instead writing this driver in Lua. The device speaks I2C and has no strict timing requirements. There isn't even any really fiddly numeric work to be done. See https://github.com/nodemcu/nodemcu-firmware/blob/release/lua_modules/mcp23017/mcp23017.lua for an example.

This is something I have considered and this can be said for a number of modules that now make up this project. For my projects I prefer to have the hardware interaction abstracted and not having to load a number of modules in Lua to complete my project.

The module is build, the documentation has been created and can be incorporated. If you prefer not to include it as such then that's fine.

[serg3295]

In the documentation, the example for the error() function is the same as for the app_version() one. It is possible that this is a mistake.

[wbvreeuwijk]

@serg3295 good catch. I updated the documentation.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[HHHartmann]

I feel we shouldn't close finished PRs. If we don't want them they still can help someone else