gpio(hx711): add driver for 24 bit ADC e.g. measure with load cells

[gen2thomas]

Solved issues and/or description of the change

• implement HX711 driver by wrapping tinygo/drivers/hx711 for gobot needs.
• solves [Serial] HX711 weight cell support #1050

Manual test

• OS and Version (Win/Mac/Linux): Linux
• Adaptor(s) and/or driver(s): tinkerboard (see example)

Checklist

• depends on WIP: add hx711 driver tinygo-org/drivers#790
• The PR's target branch is 'hybridgroup:dev'
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes (e.g. by run make test_race)
• No linter errors exist locally (e.g. by run make fmt_check)
• I have performed a self-review of my own code

If this is a new driver or adaptor:

• I have added the name to the corresponding README.md
• I have added an example to see how to setup and use it
• I have checked or build at least my new example (e.g. by run make examples_check)