feat(webui): add state creation page

pkg/webui/html/states.html

@@ -1,5 +1,11 @@
 {{ define "main" }}
 <main class="responsive" id="main">
+  <a href="/states/new">
+    <button class="small-round">
+      <i>add</i>
+      <span>New</span>
+    </button>
+  </a>
   <table class="clickable-rows no-space">
     <thead>
       <tr>

pkg/webui/html/states_new.html

@@ -0,0 +1,33 @@
+{{ define "main" }}
+<main class="responsive">
+  <form action="/states/new" enctype="multipart/form-data" method="post">
+    <fieldset>
+      <div class="field border label{{ if .PathError }} invalid{{ end }}">
+        <input autofocus
+               id="path"
+               name="path"
+               required
+               type="text"
+               value="{{ .Path }}">
+        <label for="path">Path</label>
+        {{ if .PathDuplicate }}
+        <span class="error">This path already exist</span>
+        {{ else if .PathError }}
+        <span class="error">Invalid path</span>
+        {{ else }}
+        <span class="helper">Valid URL path beginning with a /</span>
+        {{ end }}
+      </div>
+      <div class="field label border">
+        <input name="file"
+               required
+               type="file">
+        <input type="text">
+        <label>File</label>
+        <span class="helper">JSON state file</span>
+      </div>
+      <button class="small-round" type="submit" value="submit">New</button>
+    </fieldset>
+  </form>
+</main>
+{{ end }}