Windows users encounter problems running the `docker-compose` commands
to run an instance of Superset.
The reason for this is line-endings for the `*.sh` files that are
mounted and used in the `command` sections for the superset images.
Many Windows users will check the repository out with line endings set
to `CRLF`. When mounted in to the *nix-based containers, these line
endings are not understood, leading to errors such as:
```text
/usr/bin/env: bash\r: No such file or directory
```
The addition of a `.gitattributes` file resolves this issue by telling
git to always resolve these files with `LF` line endings.
+semver: fix
+ref: #10132
Maxime Beauchemin
George