feat(gatsby-plugin-google-analytics): add TS typings for OutboundLink component (#10215)

Author: tdharmon

packages/gatsby-plugin-google-analytics/index.d.ts

@@ -0,0 +1,11 @@
+import * as React from "react"
+
+interface OutboundLinkProps {
+  onClick?: (event: React.MouseEvent<HTMLAnchorElement>) => void
+}
+
+class OutboundLink extends React.Component<
+  OutboundLinkProps & React.HTMLProps<HTMLAnchorElement>,
+  any
+> {}
+export { OutboundLink }