blog(two-rule-sets): remove the post, redirect to the docs Developer Guide

The post has moved to the docs site as a Developer Guide page:
https://docs.datacontroller.io/developer-guide/two-rule-sets-one-table/

- content/blog/two-rule-sets-one-table/ is removed (the images moved to the
  docs repo, where the page now lives).
- static/two-rule-sets-one-table/index.html keeps the old URL working with a
  client-side redirect to the new page, plus a canonical link and noindex.
  A static file at that path is served the same way the removed Gatsby page
  was (both are index.html under a directory).

static/two-rule-sets-one-table/index.html

@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <title>One Table, Two Rule Sets has moved</title>
+    <link rel="canonical" href="https://docs.datacontroller.io/developer-guide/two-rule-sets-one-table/" />
+    <meta http-equiv="refresh" content="0; url=https://docs.datacontroller.io/developer-guide/two-rule-sets-one-table/" />
+    <meta name="robots" content="noindex" />
+  </head>
+  <body>
+    <p>
+      This page has moved to
+      <a href="https://docs.datacontroller.io/developer-guide/two-rule-sets-one-table/">docs.datacontroller.io</a>.
+    </p>
+  </body>
+</html>