Add domain search

Add Gist link to a simple BASH function for the API

Resolves #383

Update mail.ts

* Update .docker.env

* Update .example.env

* Update .template.env

* Add a the documentation how to configure Kutt

* Added link to official docker hub image

* Fix typo

Resolves #290, #210, #34

Resolves #357.

* Sanitize docker-compose

- remove the container names since this is not mandatory and the feature is not used.
- remove the network since all containers can communicate with each other when using docker-compose.
- add persistence to the databases to avoid the loss of data.

* Add .env file for docker 

This is a copy of the `.example.env`-file with some settings changed to work with the docker-compose file

Add the new image to the `docker-compose`-file.
See #329