feat: add app code

- journal domain package
- httpserver package
- html templates
- main.go in root dir

templates/entry.html

@@ -0,0 +1,28 @@
+{{ template "layout.html" . }}
+
+{{ define "title" }}{{ .Title }} [{{ .FormattedDate }}]{{ end }}
+
+{{ define "content" }}
+<script>
+  function deleteEntry(event) {
+    event.preventDefault();
+    if (window.confirm('Do you really want to delete this entry?')) {
+      document.getElementById('delete-entry').submit();
+    }
+  }
+</script>
+<main class="container">
+   <h1>{{ .Title }}</h1>
+   <h2>[{{ .FormattedDate }}]</h2>
+   <hr />
+   <p>
+    [<a href="/entry/{{ .ID }}/edit">Edit</a>]
+    [<a href="#" onclick="deleteEntry(event)">Delete</a>]
+   </p>
+   <form id="delete-entry" action="/entry/delete" method="POST">
+    <input type="hidden" name="id" value="{{ .ID }}">
+   </form>
+   <hr />
+   <p>{{ .HTMLContent }}</p>
+</main>
+{{ end }}