Add feature flag for opening external links in a new tab (#749)

Closes https://github.com/modrinth/knossos/issues/438

pages/index.vue

@@ -12,10 +12,12 @@
         <h1>Discover, Play, and Create Minecraft content</h1>
         <h3>
           Find enjoyable, quality content through our
-          <a href="https://github.com/modrinth" target="_blank">open-source</a>
+          <a href="https://github.com/modrinth" :target="$external()">
+            open-source
+          </a>
           modding platform built for the community. Create stuff, get paid, and
           deploy your project with our
-          <a href="https://docs.modrinth.com" target="_blank"
+          <a href="https://docs.modrinth.com" :target="$external()"
             >fully documented</a
           >
           API!
@@ -80,13 +82,15 @@
               working on giving creators more analytics, adding new types of
               projects, our launcher, and much more! If you have any more
               feature ideas, feel free to join our
-              <a href="https://discord.gg/EUHuJHt" target="_blank">Discord</a>!
+              <a href="https://discord.gg/EUHuJHt" :target="$external()">
+                Discord</a
+              >!
             </p>
             <div class="features">
               <div class="feature completed">
                 <CheckIcon />
                 <p>
-                  <a href="https://github.com/modrinth" target="_blank">
+                  <a href="https://github.com/modrinth" :target="$external()">
                     100% open source
                   </a>
                 </p>
@@ -98,7 +102,7 @@
               <div class="feature completed">
                 <CheckIcon />
                 <p>
-                  <a href="https://docs.modrinth.com" target="_blank">
+                  <a href="https://docs.modrinth.com" :target="$external()">
                     Completely documented API
                   </a>
                 </p>
@@ -193,7 +197,7 @@
             We have created an open source modding platform for the community.
             We're committed to open source so the community can trust us as
             their modding platform. Our API is
-            <a href="https://docs.modrinth.com" target="_blank"
+            <a href="https://docs.modrinth.com" :target="$external()"
               >fully documented</a
             >
             so anyone can use it. We will never add restrictions on our API!