Remove fmt.Sprintf call in attribute Render (#38) Just concatenating the strings is much faster. Before: ``` make benchmark go test -bench=. goos: darwin goarch: amd64 pkg: github.com/maragudk/gomponents BenchmarkAttr/boolean_attributes-8 8194791 139 ns/op BenchmarkAttr/name-value_attributes-8 5143292 229 ns/op PASS ok github.com/maragudk/gomponents 2.841s ``` After: ``` make benchmark go test -bench=. goos: darwin goarch: amd64 pkg: github.com/maragudk/gomponents BenchmarkAttr/boolean_attributes-8 16755404 67.0 ns/op BenchmarkAttr/name-value_attributes-8 10208625 116 ns/op PASS ok github.com/maragudk/gomponents 2.702s ```