Enabled SonarQube scanning for PRs (#1215)

## 🎟️ Tracking

https://bitwarden.atlassian.net/browse/VULN-193

## 📔 Objective

This is to enable SonarQube scanning in PRs, and not just the
main/master branches.

## ⏰ Reminders before review

- Contributor guidelines followed
- All formatters and local linters executed and passed
- Written new unit and / or integration tests where applicable
- Protected functional changes with optionality (feature flags)
- Used internationalization (i18n) for all UI strings
- CI builds passed
- Communicated to DevOps any deployment requirements
- Updated any necessary documentation (Confluence, contributing docs) or
informed the documentation
  team

## 🦮 Reviewer guidelines

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- 👍 (`:+1:`) or similar for great changes
- 📝 (`:memo:`) or ℹ️ (`:information_source:`) for notes or general info
- ❓ (`:question:`) for questions
- 🤔 (`:thinking:`) or 💭 (`:thought_balloon:`) for more open inquiry
that's not quite a confirmed
  issue and could potentially benefit from discussion
- 🎨 (`:art:`) for suggestions / improvements
- ❌ (`:x:`) or ⚠️ (`:warning:`) for more significant problems or
concerns needing attention
- 🌱 (`:seedling:`) or ♻️ (`:recycle:`) for future improvements or
indications of technical debt
- ⛏ (`:pick:`) for minor or nitpick changes

Author: mandreko-bitwarden

.github/workflows/scan.yml

@@ -74,3 +74,4 @@ jobs:
             -Dsonar.organization=${{ github.repository_owner }}
             -Dsonar.projectKey=${{ github.repository_owner }}_${{ github.event.repository.name }}
             -Dsonar.exclusions=languages/**
+            -Dsonar.pullrequest.key=${{ github.event.pull_request.number }}