Async initialization for DateFormat

pkg/intl/data/dates/symbols/sk.json

Index: pkg/intl/data/dates/symbols/sk.json
===================================================================
--- pkg/intl/data/dates/symbols/sk.json	(revision 0)
+++ pkg/intl/data/dates/symbols/sk.json	(revision 0)
@@ -0,0 +1 @@
+{"DATEFORMATS":["EEEE, d. MMMM y","d. MMMM y","d.M.yyyy","d.M.yyyy"],"NARROWWEEKDAYS":["N","P","U","S","Š","P","S"],"STANDALONESHORTMONTHS":["jan","feb","mar","apr","máj","jún","júl","aug","sep","okt","nov","dec"],"ERANAMES":["pred n.l.","n.l."],"FIRSTWEEKCUTOFFDAY":3,"NARROWMONTHS":["j","f","m","a","m","j","j","a","s","o","n","d"],"STANDALONESHORTWEEKDAYS":["ne","po","ut","st","št","pi","so"],"FIRSTDAYOFWEEK":0,"STANDALONEWEEKDAYS":["nedeľa","pondelok","utorok","streda","štvrtok","piatok","sobota"],"WEEKDAYS":["nedeľa","pondelok","utorok","streda","štvrtok","piatok","sobota"],"QUARTERS":["1. štvrťrok","2. štvrťrok","3. štvrťrok","4. štvrťrok"],"ERAS":["pred n.l.","n.l."],"MONTHS":["januára","februára","marca","apríla","mája","júna","júla","augusta","septembra","októbra","novembra","decembra"],"TIMEFORMATS":["H:mm:ss zzzz","H:mm:ss z","H:mm:ss","H:mm"],"SHORTWEEKDAYS":["ne","po","ut","st","št","pi","so"],"SHORTQUARTERS":["Q1","Q2","Q3","Q4"],"WEEKENDRANGE":[5,6],"STANDALONENARROWWEEKDAYS":["N","P","U","S","Š","P","S"],"AVAILABLEFORMATS":null,"NAME":"sk","AMPMS":["dopoludnia","popoludní"],"STANDALONEMONTHS":["január","február","marec","apríl","máj","jún","júl","august","september","október","november","december"],"SHORTMONTHS":["jan","feb","mar","apr","máj","jún","júl","aug","sep","okt","nov","dec"],"STANDALONENARROWMONTHS":["j","f","m","a","m","j","j","a","s","o","n","d"]}