feat: improve Docker configuration and detection handling (#242)

- Pass `cfg` to `envcheck.CheckIfDockerRunning` function
- Add `Docker` struct to `config.go` for Docker configuration
- Update `config.example.yaml` with `docker` configuration options
- Modify `CheckIfDockerRunning` in `docker.go` to use Docker host from config if provided

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Reviewed-on: https://gitea.com/gitea/act_runner/pulls/242
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: wxiaoguang <wxiaoguang@noreply.gitea.com>
Co-authored-by: appleboy <appleboy.tw@gmail.com>
Co-committed-by: appleboy <appleboy.tw@gmail.com>

internal/app/cmd/daemon.go

@@ -63,7 +63,7 @@ func runDaemon(ctx context.Context, configFile *string) func(cmd *cobra.Command,
 		}
 
 		if ls.RequireDocker() {
-			if err := envcheck.CheckIfDockerRunning(ctx); err != nil {
+			if err := envcheck.CheckIfDockerRunning(ctx, cfg); err != nil {
 				return err
 			}
 		}