Add plain button (#5419)

* Add plain button

* Minor syntax improvements

client/app/components/PlainButton.less

@@ -0,0 +1,22 @@
+@import (reference, less) "~@/assets/less/ant";
+
+.plain-button {
+  all: unset;
+  transition: all 0.3s cubic-bezier(0.645, 0.045, 0.355, 1);
+
+  .@{dropdown-prefix-cls}-menu-item > & {
+    width: 100%;
+    margin: -5px -12px;
+    padding: 5px 12px;
+  }
+
+  .@{menu-prefix-cls}-item > & {
+    width: 100%;
+    margin: 0 -16px;
+    padding: 0 16px;
+  }
+}
+
+.plain-button-link {
+  .btn-link();
+}

client/app/components/PlainButton.tsx

@@ -0,0 +1,20 @@
+import classNames from "classnames";
+import React from "react";
+
+import "./PlainButton.less";
+
+interface PlainButtonType extends Omit<React.ButtonHTMLAttributes<HTMLButtonElement>, "type"> {
+  type?: "link" | "button";
+}
+
+function PlainButton({ className, type, ...rest }: PlainButtonType) {
+  return (
+    <button
+      className={classNames("plain-button", "clickable", { "plain-button-link": type === "link" }, className)}
+      type="button"
+      {...rest}
+    />
+  );
+}
+
+export default PlainButton;