Twinmaker: Add info box to sample alarm dashboard

[iwysiu]

What this PR does / why we need it:
Adds a short explanation for using the sample Alarm Dashboard to the top of it

Which issue(s) this PR fixes:

Fixes #152

[github-actions]

Backend code coverage report for PR #169
No changes

[github-actions]

Frontend code coverage report for PR #169

Plugin	Main	PR	Difference
src	44.59%	44.59%	0%

[github-actions]

Levitate is-compatible report:

🔍 Resolving @grafana/data@latest...
🔍 Resolving @grafana/ui@latest...
🔍 Resolving @grafana/runtime@latest...
🔍 Resolving @grafana/e2e-selectors@latest...

🔬 Checking compatibility between ./src/module.ts and @grafana/data@9.3.6...
✔ Found @grafana/data version 8.4.11 locally

🔬 Checking compatibility between ./src/module.ts and @grafana/ui@9.3.6...
✔ Found @grafana/ui version 8.4.11 locally

🔬 Checking compatibility between ./src/module.ts and @grafana/runtime@9.3.6...
✔ Found @grafana/runtime version 8.4.11 locally

🔬 Checking compatibility between ./src/module.ts and @grafana/e2e-selectors@9.3.6...
✔ Found @grafana/e2e-selectors version 8.4.11 locally

✔️ ./src/module.ts appears to be compatible with @grafana/data,@grafana/ui,@grafana/runtime,@grafana/e2e-selectors