Worker readme

* Add common info
* Add creating worker block
* Add block about task queuing
* Add block about task scheduling
Ok. I'm not against `runtime 'go'`, but if it's preferable way, we should add info:

* how to upload go files with github or other remote dependencies (i tried to do it and all my attempts failed)
* how to upload projects with multiple files (i tried to do it and all my attempts failed)
* that we use old version of go (i think it is main reason why `runtime 'binary'` is preferrable)