[lint] Tweak editorconfig and frontend lint:

- Ignore computer generated files when linting.
- Include .mo files for consistency.
- Use multiline yaml syntax for `run` commands.

.editorconfig

@@ -20,9 +20,10 @@ block_comment_end = */
 [{bw-dev,fr-dev,LICENSE}]
 max_line_length = off
 
-[*.{csv,json,html,md,po,py,svg,tsv}]
+[*.{csv,json,html,md,mo,po,py,svg,tsv}]
 max_line_length = off
 
+# `  ` at the end of a line is a line-break in markdown
 [*.{md,markdown}]
 trim_trailing_whitespace = false
 
@@ -30,7 +31,11 @@ trim_trailing_whitespace = false
 indent_size = 2
 max_line_length = off
 
-[{package.json,yarn.lock}]
+# Computer generated files
+[{package.json,*.lock}]
 indent_size = unset
 indent_style = unset
 max_line_length = unset
+
+[*.mo]
+insert_final_newline = unset