Update pull request template and fix some ambiguities

Based on commonly seen ""mistakes"" in PR descriptions

.github/pull_request_template.md

@@ -1,14 +1,14 @@
-Resolves: *(direct link to the issue)*
+Resolves: #NNNNN <!-- Replace `NNNNN` with a GitHub issue number, or a direct link if the issue is not on GitHub -->
 
-*(short description of the changes and the motivation to make the changes)*
+<!-- Add a short description of and motivation for the changes here -->
 
-<!-- Use "x" to fill the checkboxes below like [x] -->
+<!-- Replace `[ ]` with `[x]` to fill the checkboxes below -->
 
-- [ ] I signed [CLA](https://musescore.org/en/cla)
-- [ ] I made sure the code in the PR follows [the coding rules](https://github.com/musescore/MuseScore/wiki/CodeGuidelines)
-- [ ] I made sure the code compiles on my machine
-- [ ] I made sure there are no unnecessary changes in the code
-- [ ] I made sure the title of the PR reflects the core meaning of the issue you are solving
-- [ ] I made sure the commit message(s) contain a description and answer the question "Why do those changes fix that particular issue?" or "Why are those changes really necessary as improvements?"
-- [ ] I made sure the commit message title starts with "fix #424242:" if there is a related issue
-- [ ] I created the test (mtest, vtest, script test) to verify the changes I made
+- [ ] I signed the [CLA](https://musescore.org/en/cla)
+- [ ] The title of the PR describes the problem it addresses
+- [ ] Each commit's message describes its purpose and effects, and references the issue it resolves
+- [ ] If changes are extensive, there is a sequence of easily reviewable commits
+- [ ] The code in the PR follows [the coding rules](https://github.com/musescore/MuseScore/wiki/CodeGuidelines)
+- [ ] There are no unnecessary changes
+- [ ] The code compiles and runs on my machine, preferably after each commit individually
+- [ ] I created a unit test or vtest to verify the changes I made (if applicable)