Add .editorconfig file

[egillespie]

Describe the solution you'd like

Create a .editorconfig file with content to match the one in cityzen-client-vue. This will offer a standardized, (mostly) editor-agnostic way to enforce basic coding styles such as 2-space indentation and trimming whitespace at the end of lines.

Describe alternatives you've considered

Right now some of the supported coding styles are in .vsocde/settings.json.