fix(app.py): add function to insert custom CSS for the app
fix(l10n/de/main.ftl): fix typo in translation
fix(l10n/fr/main.ftl): fix typo in translation
fix(l10n/id/main.ftl): fix typo in translation
fix(mangosteen/column_definitions.py): update format for number columns
fix(mangosteen/gridify.py): update display for number columns and add custom CSS class for text columns
feat(static/app.css): add custom CSS for text columns in the app