Update changelog and version after v2.20.0

CHANGELOG.md

@@ -1,5 +1,9 @@
 # CodeQL Action Changelog
 
+## [UNRELEASED]
+
+No user facing changes.
+
 ## 2.20.0 - 13 Jun 2023
 
 - Bump the version of the Action to 2.20.0. This ensures that users who received a Dependabot upgrade to [`cdcdbb5`](https://github.com/github/codeql-action/commit/cdcdbb579706841c47f7063dda365e292e5cad7a), which was mistakenly marked as Action version 2.13.4, continue to receive updates to the CodeQL Action. Full details in [#1729](https://github.com/github/codeql-action/pull/1729)

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "codeql",
-  "version": "2.20.0",
+  "version": "2.20.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "codeql",
-      "version": "2.20.0",
+      "version": "2.20.1",
       "license": "MIT",
       "dependencies": {
         "@actions/artifact": "^1.1.0",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "codeql",
-  "version": "2.20.0",
+  "version": "2.20.1",
   "private": true,
   "description": "CodeQL action",
   "scripts": {