Use shared Editorconfig settings

All @bisq-network repositories have a `.editorconfig` file, and all text editors worth using have support for [Editorconfig](http://editorconfig.org/). Please make sure your text editor is properly configured to read and respect these files. They make sure that we all use a common whitespace conventions, e.g. 4-space indentation, strip trailing whitespace, newlines at end of file, etc.

Start by reading the repository's .editorconfig file and the EditorConfig documentation linked in the issue. Configure a supported text editor to respect those settings, then verify that indentation, trailing whitespace, and final-newline behavior match the shared conventions.

Written by the indexing model from the issue text.