feat(web/blog): Add Nix-based static blog generator

This introduces a derivation which builds an instance of nginx
statically serving my blog posts, though as of now no indexes are
being generated and no XML feed is available.

This is just the initial draft of this setup and not yet what shall be
yielded in the end.

web/blog/static/blog.css

@@ -0,0 +1,35 @@
+body {
+    margin: 40px auto;
+    max-width: 650px;
+    line-height: 1.6;
+    font-size: 18px;
+    color: #383838;
+    padding: 0 10px
+}
+h1, h2, h3 {
+    line-height: 1.2
+}
+.footer {
+    text-align: right;
+}
+.lod {
+    text-align: center;
+}
+.unstyled-link {
+    color: inherit;
+    text-decoration: none;
+}
+.uncoloured-link {
+    color: inherit;
+}
+.date {
+    text-align: right;
+    font-style: italic;
+    float: right;
+}
+.inline {
+    display: inline;
+}
+.navigation {
+    text-align: center;
+}