Xontrib-macro-lib

* Now you can run `xontrib load macrolib` in interactive mode and use completion with `with! macrolib.<Tab>`.
* Added `macrolib.data.Write` and `macrolib.data.Replace`.
* `macrolib.run_once.RunOnce` renamed to `macrolib.run.Once`.

Maintenance

* Added `xontrib.macro_lib.data.Write`.

* Added `data.JsonBlock`
* Added `Block` example

Fix docs.

Two macro:
* RunOnce
* RunInXonshDocker