Add .env file

[ValentinaSukonina]

To have working docker container we need to provide information and pathway for the database

[Ebyrdeu]

The reason I added .env to ignore and .env-example to the root of the project is because this is how it's usually done. Each person needs to create their own .env file based on .env-example, and it should not be exposed at any point in the project's life.