style(predlozhnik): make the page look a bit more inviting

with some sprinkling of CSS and some different button classes, this
doesn't look half bad!

Change-Id: I49a3af4a77ce58713c735b2401b807062a3efb21
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5989
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

users/tazjin/predlozhnik/index.css

@@ -0,0 +1,29 @@
+body {
+    max-width: 800px;
+    margin: 40px auto;
+}
+
+#header {
+    display: flex;
+    flex-direction: column;
+}
+
+.btn.btn-ghost:disabled {
+    border-color: #9f9f9f;
+    color: #9f9f9f;
+}
+
+#predlogi,#padezhi {
+    display: flex;
+    flex-direction: row;
+    flex-wrap: wrap;
+}
+
+.btn {
+    margin: 3px;
+    flex-grow: 1;
+}
+
+.footer {
+    text-align: right;
+}