Fix filtering for different tags in sequence

If the posts were filtered by one tag first, and then another, the
displayed posts would only be those matching *both* tags, without this
being indicated in the url (and different after a reload).

go/blog/blog.go

@@ -312,7 +312,9 @@ func main() {
					}
				}
			}
			if (!matches) {
			if (matches) {
				article.classList.remove("does-not-match");
			} else {
				article.classList.add("does-not-match");
			}
		}