Normalize whitespace in source files

Ensure that no source files have trailing whitespace at end of lines and ensure that all files end with a single trailing newline.

This also adds Github Actions to enforce whitespace conventions.

src-ui/src/app/data/paperless-correspondent.ts

@@ -1,7 +1,7 @@
 import { MatchingModel } from './matching-model';
 
 export interface PaperlessCorrespondent extends MatchingModel {
-  
+
   last_correspondence?: Date
 
 }