Use own name for languages rather than English one

For now this only comes for languages in which a translation of musdb
exists.

src/MDLanguagesSet.php

@@ -253,7 +253,7 @@ final class MDLanguagesSet {
         'fi' => 'Finnish',
         'fj' => 'Fijian',
         'fo' => 'Faroese',
-        'fr' => 'French',
+        'fr' => 'Français',
         'fy' => 'Western Frisian',
         'ga' => 'Irish',
         'gd' => 'Scottish Gaelic; Gaelic',
@@ -336,14 +336,14 @@ final class MDLanguagesSet {
         'os' => 'Ossetian, Ossetic',
         'pa' => 'Panjabi, Punjabi',
         'pi' => 'Pali',
-        'pl' => 'Polish',
+        'pl' => 'Polski',
         'ps' => 'Pashto, Pushto',
         'pt' => 'Português',
         'qu' => 'Quechua',
         'rm' => 'Romansh',
         'rn' => 'Kirundi',
         'ro' => 'Română',
-        'ru' => 'Russian',
+        'ru' => 'Русский',
         'rw' => 'Kinyarwanda',
         'sa' => 'Sanskrit (संस्कृत)',
         'sc' => 'Sardinian',
@@ -378,7 +378,7 @@ final class MDLanguagesSet {
         'tw' => 'Twi',
         'ty' => 'Tahitian',
         'ug' => 'Uighur, Uyghur',
-        'uk' => 'Ukrainian',
+        'uk' => 'Українська',
         'ur' => 'اردو',
         'uz' => 'Uzbek',
         've' => 'Venda',