Migrate to grafana create-plugin

[Benedikt Seidl]

After updating dependencies yarn builds shows the following warning:

$ grafana-toolkit plugin:build

⚠  DEPRECATED. This command is deprecated and will be removed in v10. ⚠
Please migrate to grafana create-plugin https://github.com/grafana/plugin-tools/tree/main/packages/create-plugin

• https://github.com/grafana/plugin-tools/tree/main/packages/create-plugin#migrate-your-existing-plugin
• https://grafana.github.io/plugin-tools/docs/migrating-from-toolkit/