Update Code to 1.90.0 (#6824)

Additionally:

- Update Node to 20.11.1
- Update documentation
- Disable extension signature verification

This works around an issue where the Open VSX is not returning the
expected zip.  Verification is skipped later anyway because
@vscode/vsce-sign is missing in the OSS version.

package.json

@@ -44,7 +44,7 @@
     "@types/express": "^4.17.17",
     "@types/http-proxy": "1.17.7",
     "@types/js-yaml": "^4.0.6",
-    "@types/node": "^18.0.0",
+    "@types/node": "20.x",
     "@types/pem": "^1.14.1",
     "@types/proxy-from-env": "^1.0.1",
     "@types/safe-compare": "^1.1.0",
@@ -88,7 +88,7 @@
     "xdg-basedir": "^4.0.0"
   },
   "resolutions": {
-    "@types/node": "^18.0.0"
+    "@types/node": "20.x"
   },
   "bin": {
     "code-server": "out/node/entry.js"
@@ -103,7 +103,7 @@
     "remote-development"
   ],
   "engines": {
-    "node": "18"
+    "node": "20"
   },
   "jest": {
     "transform": {