LibGUI+HackStudio: Associate new icons with their extensions

Author: https://github.com/thankyouverycool
Commit: 45901d4141
Pull-request: https://github.com/SerenityOS/serenity/pull/3310

Libraries/LibGUI/FileIconProvider.cpp

@@ -34,6 +34,8 @@ namespace GUI {
 
 #define ENUMERATE_FILETYPES(F) \
     F(cplusplus, ".cpp")       \
+    F(form, ".frm")            \
+    F(hackstudio, ".hsp")      \
     F(header, ".h")            \
     F(html, ".html")           \
     F(image, ".png")           \