Added Wiki link in ISSUE_TEMPLATE.md (#496)

Author: Geolim4

.github/ISSUE_TEMPLATE.md

@@ -6,4 +6,5 @@ Operating system: ` ...replace me... `
 
 #### Issue description:
 
-> ...Your description goes here...
+> ... Your description goes here ... 
+... You can also read the [wiki](https://github.com/PHPSocialNetwork/phpfastcache/wiki) ...