Update template with latest recommendations

.github/ISSUE_TEMPLATE.md

@@ -1,13 +1,17 @@
 # READ CAREFULLY BEFORE SUBMITTING
 
-**This list is for avoiding duplicated issues, if your issue isn't listed, you should remove this and continue.**
+Whilst we are happy for issues to be raised, we do strongly recommend that you investigate as much as possible
+and provide a Git Pull Request with a suggested fix.
 
-- The theme doesn't work in a distribution that have a GTK+ 3 version lower than 3.14.
-  - Arc only supports versions since 3.14, you should update to latest versions.
+**The list below is for avoiding duplicated issues; if your issue isn't listed, you should remove this and continue.**
+
+- The theme doesn't work in a distribution that have a GTK+ 3 version lower than 3.18.
+  - Arc only supports versions since 3.18, you should update to latest versions.
 - The theme is broken after a major GTK+ 3 update (i.e. 3.18 to 3.20 or 3.20 to 3.22).
   - Update the package or install from sources.
 - The theme is broken after installing from sources.
-  - Possibly a bug on GTK+ 3 version checking, use `--with-gnome=<version>` flag with `./autogen.sh`.
+  - Possibly a bug on GTK+ 3 version checking, use `--with-gtk3=<version>` flag with `./autogen.sh`.
+  - Possibly a bug with GNOME-Shell version checking, use `--with-gnome-shell=<version>` flag with `./autogen.sh`.
 - Theme isn't transparent on GNOME applications without CSD (i.e. Ubuntu's applications).
   - Transparency isn't supported for non-CSD applications.
 - Theme doesn't build from AUR in Arch/Manjaro and others.
@@ -29,5 +33,5 @@
 - Arc version/commit (don't put "latest"):
 - GTK+ 3 version:
   - Murrine engine version:
-  - `gnome-themes-standard` version:
+  - `gnome-themes-extras` version:
 - Installation method (package or source):