Links: extract external navigation links component

The Header and Footer shared some duplicated code related to external
links. We moved the markup and CSS into a separate Links component to
DRY it up.

We currently apply a 'line-through' style to the Figma links, since they
are not yet implemented. This is a visual treatment only an needs fixed
before production release!

src/components/Links/Links.tsx

@@ -0,0 +1,80 @@
+import React from "react";
+import { OutboundLink } from "react-ga";
+import { ArrowElbowDownRight } from "phosphor-react";
+
+import "./Links.css";
+
+interface LinksProps {}
+
+const Links: React.FC<LinksProps> = () => {
+  return (
+    <div className="links">
+      <div>
+        <ArrowElbowDownRight size={24} />
+        <OutboundLink
+          className="nav-link"
+          to="https://phosphoricons.com/assets/phosphor-icons.zip"
+          eventLabel="Download all"
+          download
+          type="application/zip"
+        >
+          Download all
+        </OutboundLink>
+      </div>
+      <div>
+        <ArrowElbowDownRight size={24} />
+        <OutboundLink
+          className="nav-link"
+          to="#"
+          eventLabel="Figma library"
+          style={{ textDecoration: "line-through" }}
+        >
+          Figma library
+        </OutboundLink>
+      </div>
+      <div>
+        <ArrowElbowDownRight size={24} />
+        <OutboundLink
+          className="nav-link"
+          to="#"
+          eventLabel="Figma plugin"
+          style={{ textDecoration: "line-through" }}
+        >
+          Figma plugin
+        </OutboundLink>
+      </div>
+      <div>
+        <ArrowElbowDownRight size={24} />
+        <a
+          className="nav-link"
+          href="https://github.com/phosphor-icons/phosphor-web/issues"
+        >
+          Request an icon
+        </a>
+      </div>
+      <div>
+        <ArrowElbowDownRight size={24} />
+        <span>
+          <a className="nav-link" href="https://paypal.me/minoraxis">
+            Donate on PayPal
+          </a>
+          {" / "}
+          <a className="nav-link" href="https://patreon.com/phosphoricons">
+            Patreon
+          </a>
+        </span>
+      </div>
+      <div>
+        <ArrowElbowDownRight size={24} />
+        <a
+          className="nav-link"
+          href="https://github.com/phosphor-icons/phosphor-web"
+        >
+          Github
+        </a>
+      </div>
+    </div>
+  );
+};
+
+export default Links;