added *_wpftmp.csproj to gitignore (#2287)

Author: TysonMN

.gitignore

@@ -1,5 +1,7 @@
 ## Ignore Visual Studio temporary files, build results, and
 ## files generated by popular Visual Studio add-ons.
+##
+## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore
 
 # User-specific files
 *.suo
@@ -58,6 +60,7 @@ dlldata.c
 *.tlh
 *.tmp
 *.tmp_proj
+*_wpftmp.csproj
 *.log
 *.vspscc
 *.vssscc