Group element helpers in different files (#21)

According to the section at https://developer.mozilla.org/en-US/docs/Web/HTML/Element

1 files changed, 15 insertions, 0 deletions

diff --git a/attr/form.go b/attr/form.go
new file mode 100644
index 0000000..b3eec05
--- /dev/null
+++ b/attr/form.go
@@ -0,0 +1,15 @@
+package attr
+
+import (
+	g "github.com/maragudk/gomponents"
+)
+
+// Placeholder returns an attribute with name "placeholder" and the given value.
+func Placeholder(v string) g.Node {
+	return g.Attr("placeholder", v)
+}
+
+// Required returns an attribute with name "required".
+func Required() g.Node {
+	return g.Attr("required")
+}