chore: Move default PR template to correct dir

.github/pull_request_template.md

@@ -0,0 +1,21 @@
+*Thank you so much for your contribution to FluffyChat ❤️❤️❤️*
+
+Please make sure that your Pull Request meet the following **acceptance criteria**:
+
+- [ ] Code formatting and import sorting has been done with `dart format lib/ test/` and `dart run import_sorter:main --no-comments`
+- [ ] The commit message uses the format of [Conventional Commits](https://www.conventionalcommits.org)
+- [ ] The commit message describes what has been changed, why it has been changed and how it has been changed
+- [ ] Every new feature or change of the design/GUI is linked to an approved design proposal in an issue
+- [ ] Every new feature in the app or the build system has a strategy how this will be tested and maintained from now on for every release, e.g. a volunteer who takes over maintainership
+
+
+### Pull Request has been tested on:
+
+- [ ] Android
+- [ ] iOS
+- [ ] Browser (Chromium based)
+- [ ] Browser (Firefox based)
+- [ ] Browser (WebKit based)
+- [ ] Desktop Linux
+- [ ] Desktop Windows
+- [ ] Desktop macOS