Keep GitHub Actions up to date with GitHub's Dependabot

[cclauss]

Fixes the 16 software supply chain safety warnings at the bottom right of https://github.com/FluidSynth/fluidsynth/actions/runs/8767406884

• Keeping your actions up to date with Dependabot
• Configuration options for the dependabot.yml file - package-ecosystem

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[cclauss]

Generated:

• 1319