Support for DART WZ-S formaldehyde sensor

[bbluvgg]

When researching formaldehyde sensors recently, I found that the DART WZ-S has high precision, comes pre-calibrated, and offers good accuracy.

As ESPHome now fully requires using external components, I discovered a well-developed external component code repository on Gitee. However, after placing the files according to specifications, the ESPHome Builder interface shows "Platform not found: 'sensor.dart'". I hope someone can test whether this compiles successfully and help answer my question.

Sorry if this is not the right place to post this - please let me know if I should post elsewhere.

I have uploaded the relevant files to my repository and ask the community to review them. Please help verify if these implementations correctly integrate the DART WZ-S sensor into ESPHome via external_components.

https://github.com/bbluvgg/wz-s/

`external_components:

• source: type: local path: my_components components: [dart]

uart:

• id: utt2 tx_pin: 18 rx_pin: 5 baud_rate: 9600

sensor:

• platform: dart uart_id: utt2 formaldehyde: name: "DART Formaldehyde" unit_of_measurement: "µg/m³" accuracy_decimals: 2 update_interval: 20s`

[synodriver]

I made a small change so it compiles on my machine, note that this sensor also reports a ppb value.