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.css

@@ -0,0 +1,41 @@
+.links {
+  display: flex;
+  flex-flow: column wrap;
+  align-content: flex-start;
+  align-items: flex-start;
+  justify-content: center;
+  /* column-gap: 72px; */
+  /* -webkit-column-gap: 72px; */
+  margin: 32px 0 64px;
+  max-height: 144px;
+}
+
+.links > div {
+  margin: 0 72px 24px 0;
+  display: flex;
+  align-items: center;
+}
+
+.links svg {
+  margin-right: 12px;
+}
+
+a.nav-link {
+  text-decoration: none;
+  position: relative;
+  color: black;
+}
+
+a.nav-link:after {
+  content: "";
+  position: absolute;
+  bottom: -2px;
+  left: 0;
+  width: 0%;
+  border-bottom: 1px solid black;
+  transition: 0.2s;
+}
+
+a.nav-link:hover:after {
+  width: 100%;
+}

src/components/Links/Links.tsx

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+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;