version history MVP

implement basic version history support; there's now an icon in the footer that lets you see the previous versions and their sources
I'm a bit worried about spoilers but honestly it's yet another way to hint yourself at the cool secrets so I don't mind

static/css/history.css

@@ -0,0 +1,27 @@
+.version-history {
+
+    &>ul.commits {
+        --recursive-mono: 1;
+
+        list-style: none;
+        padding-left: 0;
+
+        &>li {
+            padding-top: 0.2rem;
+            padding-bottom: 0.2rem;
+
+            display: grid;
+            grid-template-columns: 4em min-content auto;
+            align-items: start;
+            gap: 0.5em;
+
+            &>.revision-number {
+                justify-self: end;
+            }
+
+            details>summary {
+                cursor: pointer;
+            }
+        }
+    }
+}