Add runner name to log (#37)

User can get the name of the runner that executed the specified job.
![image](/attachments/61328f68-7223-4345-85c7-ac08781e81db)

Co-authored-by: Zettat123 <zettat123@gmail.com>
Reviewed-on: https://gitea.com/gitea/act_runner/pulls/37
Reviewed-by: Jason Song <i@wolfogre.com>
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Zettat123 <zettat123@noreply.gitea.io>
Co-committed-by: Zettat123 <zettat123@noreply.gitea.io>

config/config.go

@@ -65,6 +65,9 @@ func FromEnviron() (Config, error) {
 		if runner.UUID != "" {
 			cfg.Runner.UUID = runner.UUID
 		}
+		if runner.Name != "" {
+			cfg.Runner.Name = runner.Name
+		}
 		if runner.Token != "" {
 			cfg.Runner.Token = runner.Token
 		}