chore: Add "increment chart version" to pull request checklist (mesosphere#751)

Co-authored-by: Alejandro Escobar <[email protected]>

Author: dlipovetsky

.github/PULL_REQUEST_TEMPLATE.md

@@ -21,6 +21,7 @@ Enter your extended release note in the block below. If the PR requires addition
 
 **Checklist**
 
+* [ ] *If a chart is changed, the chart version is correctly incremented.*
 * [ ] The commit message explains the changes and why are needed.
 * [ ] The code builds and passes lint/style checks locally.
 * [ ] The relevant subset of integration tests pass locally.