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-document-metadata.ts

@@ -1,5 +1,5 @@
 export interface PaperlessDocumentMetadata {
-    
+
   original_checksum?: string
 
   archived_checksum?: string
@@ -10,4 +10,4 @@ export interface PaperlessDocumentMetadata {
 
   has_archive_version?: boolean
 
-}
+}