Add support for adding new files to F# web project (#3203)

This fixes the very long-standing issue where trying to add a new file to an F# Web project
opens a window with no file templates available.

See for example here for the workaround that was required for VS up to 2015:
http://bloggemdano.blogspot.fr/2013/11/adding-new-items-to-pure-f-aspnet.html

vsintegration/Vsix/RegisterFsharpPackage.pkgdef

@@ -23,6 +23,9 @@
 [$RootKey$\Projects\{A1591282-1198-4647-A2B1-27E5FF5F6F3B}\LanguageTemplates]
 "{F2A71F9B-5D33-465A-A702-920D77279786}"="{76B279E8-36ED-494E-B145-5344F8DEFCB6}"
 
+[$RootKey$\Projects\{349C5851-65DF-11DA-9384-00065B846F21}\LanguageTemplates]
+"{F2A71F9B-5D33-465A-A702-920D77279786}"="{76B279E8-36ED-494E-B145-5344F8DEFCB6}"
+
 [$RootKey$\Projects\{76B279E8-36ED-494E-B145-5344F8DEFCB6}]
 "Language(VsTemplate)"="FSharp"
 "Package"="{91A04A73-4F2C-4E7C-AD38-C1A68E7DA05C}"