feat: use pr template

based on https://github.com/ScratchAddons/ScratchAddons/blob/master/.github/pull_request_template.md?plain=1

Author: faretek1

.github/pull_request_template.md

@@ -0,0 +1,18 @@
+<!-- Thanks for contributing to scratchattach! -->
+
+Solves issue #
+<!-- 
+Give the issue that this solves from:
+https://github.com/TimMcCool/scratchattach/issues
+-->
+
+### Changes
+<!-- 
+Give details about your PR,
+e.g. names of functions you added, and/or a brief overview of how it internally works
+-->
+
+### Any other notes of interest:
+<!--
+Any other context, e.g. minor unrelated changes
+-->