Add support for Occitan and Sinhala.

src/components/PreferencesPage.vue

@@ -449,6 +449,7 @@ export default {
                 { code: "ml", name: "മലയാളം" },
                 { code: "nb_NO", name: "Norwegian Bokmål" },
                 { code: "nl", name: "Nederlands" },
+                { code: "oc", name: "Occitan" },
                 { code: "or", name: "ଓଡ଼ିଆ" },
                 { code: "pl", name: "Polski" },
                 { code: "pt", name: "Português" },
@@ -456,6 +457,7 @@ export default {
                 { code: "pt_BR", name: "Português (Brasil)" },
                 { code: "ro", name: "Română" },
                 { code: "ru", name: "Русский" },
+                { code: "si", name: "සිංහල" },
                 { code: "sr", name: "Српски" },
                 { code: "sv", name: "Svenska" },
                 { code: "ta", name: "தமிழ்" },