Update list of RTL languages

[nickvergessen]

isRTL is not fully reporting all languages as RTL that the server has listed as RTL:

As per discussion in #801 and chat, the following languages should be listed as RTL:

$rtlLanguages = [
	'ar', // Arabic
	'fa', // Persian
	'he', // Hebrew
	'ps', // Pashto,
	'ug', // 'Uyghurche / Uyghur
	'ur_PK', // Urdu
];

Others can be listed, but at least those should be, but ur_PK which will be available as ur-PK in the head lang attribute is missing.

[nickvergessen]

Also the function currently seems to consider locale for uz-AF but we agreed that RTL handling should be language based.