feat: add markdown help on edit page rather than linking out

frontend/src/routes/edit/MarkdownHelp.svelte

@@ -0,0 +1,47 @@
+<script lang="ts">
+  import { Icon, Modal } from "sveltestrap";
+
+  let isOpen = false;
+  const toggle = () => (isOpen = !isOpen);
+</script>
+
+<Icon name="info-circle-fill" aria-hidden /> Your bio supports limited
+<!-- svelte-ignore a11y-invalid-attribute -->
+<a class="text-reset" href="" on:click={toggle}>Markdown</a>.
+
+<Modal header="Markdown help" body {isOpen} {toggle}>
+  <p>
+    Markdown is a simple way to format text, using symbols like <code>*</code>, <code>_</code>, and
+    <code>`</code>. If you have used Discord before, formatting works the same as there, just with a
+    couple different options.
+  </p>
+  <hr />
+  <p>Type <code>*Italic*</code> or <code>_Italic_</code> to get <em>Italic</em></p>
+  <hr />
+  <p>Type <code>**Bold**</code> or <code>__Bold__</code> to get <strong>Bold</strong></p>
+  <hr />
+  <p>Use at least three dashes <code>---</code> on a separate line to add a horizontal rule:</p>
+  <hr class="m-3" />
+  <hr />
+  <p>Type <code>`Inline code`</code> to get <code>Inline code</code></p>
+  <p>Use three backticks to make a code block:</p>
+  <pre><code>```<br />print("Code here")<br />```</code></pre>
+  <hr />
+  <p>Type</p>
+  <pre><code>* List<br />* List<br />* List</code></pre>
+  <p>to get</p>
+  <ul>
+    <li>List</li>
+    <li>List</li>
+    <li>List</li>
+  </ul>
+  <hr />
+  <p>Type</p>
+  <pre><code>1. List<br />2. List<br />3. List</code></pre>
+  <p>to get</p>
+  <ol>
+    <li>List</li>
+    <li>List</li>
+    <li>List</li>
+  </ol>
+</Modal>