Add support for getting all devices

[guyluz11]

I would like to implement this package in my open-source smart home system CyBear Jinni, but it will be drastically better and more convenient if I am able to show the user all of his devices without his need to search where to get the id in the app and add all of the ids one by one.

https://github.com/ianmaciel/dart_ewelink_api/blob/b5d945ae7c4b7ee8304e34a93462f63b07e17101/example/main.dart#L39

[ianmaciel]

I won't have time to work on this library soon.

Wouldn't you like to open a PR?

[guyluz11]

Probably in the future, currently working on adding xiaomi device support with the help of another package.

[guyluz11]

Found where the npm package that we are based on is doing the call to get all devices

Doc: https://github.com/skydiver/ewelink-api/blob/master/docs/available-methods/getdevices.md

Call in code: https://github.com/skydiver/ewelink-api/blob/master/src/mixins/getDevices.js

[ianmaciel]

Contradicting myself I have just created the method to get all devices. https://github.com/ianmaciel/dart_ewelink_api/pull/15

[guyluz11]

That's so cool of you, thanks.

Will start implementing this package into cbj sooner than expected 😆

[ianmaciel]

Would you like to review?

[guyluz11]

Done