docs: PR template — add Description section + fix rebase target to dev (#1010)

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -4,6 +4,10 @@
 
 Fixes #
 
+## Description
+
+<!-- Explain in your own words what this PR does and how it works at a high level. -->
+
 ## Type of Change
 
 - [ ] 🐛 Bug fix
@@ -13,10 +17,6 @@ Fixes #
 - [ ] ✅ Tests
 - [ ] 🔧 CI / chore
 
-## What changed
-
-<!-- What was wrong and what this PR does about it. Link the root cause if known. -->
-
 ## How to test
 
 <!-- Steps to verify. For UI: which screen + which emulator/device API level. For WS: which RPC. -->
@@ -27,7 +27,7 @@ Fixes #
 
 ## Checklist
 
-- [ ] Branch rebased onto `main` (`git rebase origin/main`)
+- [ ] Branch rebased onto `dev` (`git rebase origin/dev`)
 - [ ] `./gradlew ktlintCheck` passes (ran `ktlintFormat` first)
 - [ ] `./gradlew testDebugUnitTest` green (or CI unit-tests job)
 - [ ] `checkColorLiterals` passes (no hardcoded Color outside theme/)