Add bug report template

Author: mglaman

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,19 @@
+---
+name: Bug report
+about: Something isn't working right
+title: ''
+labels: bug
+assignees: ''
+
+---
+
+# Bug report
+
+<!-- Before reporting an issue please check that you are using the latest PHPStan and phpstan-drupal versions! -->
+<!-- composer update phpstan/phpstan mglaman/phpstan-drupal -->
+
+<!-- Please describe your problem here. -->
+
+### Code snippet that reproduces the problem
+
+<!-- Code example or link to public code scanned -->