[Technical debt] Consider configuring the workspace to specify the recommended line length for `dart format`

[navaronbracke]

I currently have dart format set to formatting to 120 characters per line, globally in my Visual Studio Code user settings.
However, the default formatting for Dart projects is 80 characters per line.

We should enforce the line length for the project's Dart files.
In Visual Studio Code, adding this setting to the .vscode folder/settings file should do it.
Not sure about other editors though.