fix: improve language docs + string parsing

testfiles/dict/gen_lang_names.js

@@ -0,0 +1,16 @@
+const fs = require("fs");
+
+const dict = JSON.parse(fs.readFileSync("dictionary.json"));
+
+const intl = new Intl.DisplayNames(["en"], { type: "language" });
+
+let langs = Object.keys(dict);
+Object.values(dict).forEach(entry => {
+  if (entry.equivalent) {
+    langs.push(...entry.equivalent);
+  }
+});
+langs.sort();
+
+const res = Object.fromEntries(langs.map((l) => [l, intl.of(l)]));
+fs.writeFileSync("lang_names.json", JSON.stringify(res, null, 2));