Made sure that 3 letter languages are also handled

src/i18n.js

@@ -66,7 +66,7 @@ export function currentLocale() {
     const potentialLocales = [ localStorage.locale, navigator.language, ...navigator.languages ];
     const availableLocales = potentialLocales
         .filter(l => !!l)
-        .map(l => l.substring(0, 2) in messages ? l.substring(0, 2) : l)
+        .map(l => l.split("-")[0] in messages ? l.split("-")[0] : l)
         .filter(l => l in messages);
     return availableLocales[0] || "en";
 }

test/cypress/unit/i18n.spec.js

@@ -46,6 +46,12 @@ describe("Test i18n.js", () => {
         setLanguages(['abc', 'en-US', 'pl', 'ja']);
         expect(currentLocale()).equal("en");
 
+        setLanguages(['fil-PH', 'pl']);
+        expect(currentLocale()).equal("pl");
+
+        setLanguages(['shi-Latn-MA', 'pl']);
+        expect(currentLocale()).equal("pl");
+
         setLanguages(['pl']);
         localStorage.locale = "ja-ZZ";
         expect(currentLocale()).equal("ja");