feat(viewer): mode pretty print avec coloration syntaxique et numeros de ligne pour fichiers texte (#89)

frontend/locales/en.json

@@ -1687,6 +1687,8 @@
   "viewer.download": "Download",
   "viewer.download_md": "Download as .md",
   "viewer.download_file": "Download file",
+  "viewer.pretty": "Pretty",
+  "viewer.pretty_title": "Formatted mode: colors and line numbers",
   "viewer.download_pdf": "Download as PDF",
   "viewer.edit": "Edit",
   "viewer.error": "Loading error",

frontend/locales/fr.json

@@ -1687,6 +1687,8 @@
   "viewer.download": "Télécharger",
   "viewer.download_md": "Télécharger en .md",
   "viewer.download_file": "Télécharger le fichier",
+  "viewer.pretty": "Pretty",
+  "viewer.pretty_title": "Mode formaté : couleurs et numéros de ligne",
   "viewer.download_pdf": "Télécharger en PDF",
   "viewer.edit": "Éditer",
   "viewer.error": "Erreur de chargement",