update vxserver.dev to fsdproject.org

fsdproject.org/include/footer.lua

@@ -0,0 +1,13 @@
+local footer = {}
+
+footer.render = function(std)
+    return table.concat({
+	std.h2("Other resources"),
+	std.tl({
+		std.external("https://git.vxserver.dev/fSD", "Git Trees"),
+		std.external("https://docs.vxserver.dev", "Documentation"),
+	}),
+})
+end
+
+return footer