[lint] Tweak editorconfig and frontend lint:

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

.github/workflows/lint-frontend.yaml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it.
       - uses: actions/checkout@v2
 
       - name: Install modules
@@ -26,8 +26,13 @@ jobs:
 
       # See .stylelintignore for files that are not linted.
       - name: Run stylelint
-        run: yarn stylelint bookwyrm/static/**/*.css --report-needless-disables --report-invalid-scope-disables
+        run: >
+          yarn stylelint bookwyrm/static/**/*.css \
+            --report-needless-disables \
+            --report-invalid-scope-disables
 
       # See .eslintignore for files that are not linted.
       - name: Run ESLint
-        run: yarn eslint bookwyrm/static --ext .js,.jsx,.ts,.tsx
+        run: >
+          yarn eslint bookwyrm/static \
+            --ext .js,.jsx,.ts,.tsx