Add v1.20 to manifest (coder#416)

Katie Horne · web-flow · commit 56159e8ff003 · 2021-06-17T16:50:03.000-05:00
diff --git a/manifest.json b/manifest.json
@@ -1,5 +1,5 @@
 {
-  "versions": ["v1.19", "v1.18", "v1.17"],
+  "versions": ["v1.20", "v1.19", "v1.18", "v1.17"],
   "routes": [
     {
       "path": "./index.md",
