Web UI redesign

* Fixed up max-width
  Instead of using relative metric like 90rem, switched over to
  pixels. This also decreases the section so my browser won't struggle
  as much with it.
* Added proper outline
  Instead of using browser's default, I declare blue-ish outline
  manually.
* Add borders to elements
  Inspired by Sourcehut.

static/style.css

@@ -7,7 +7,7 @@ body {
 }
 
 .main-section {
-  max-width: 90rem;
+  max-width: 900px;
   margin: 5px auto;
 }
 
@@ -28,14 +28,26 @@ body {
 }
 
 .form__input,
-.textarea,
-.translation {
+.textarea {
   font-size: 1rem;
   padding: 4px;
+  border: 2px solid #888888;
 }
 
 .form__button {
   padding: 4px 10px;
+  border: 2px solid #888888;
+}
+
+.form__input:focus,
+.textarea:focus,
+.form__button:focus {
+  outline: 2px solid #5d94ff;
+}
+
+.translation {
+  font-size: 1rem;
+  padding: 4px;
 }
 
 .textarea {