PUV - add manifeset file which calls out tgz_bundle name, script version, and signature

File can be named `cx-manifest.json`. Ask is to contain:
1. tgz name
2. version of script
3. signature for validation on repo upload

```bash
# cat cx-manifest.json
{
"name": "cx-pre-upgrade-validation.tgz",
"fullVersion": "2.5.1",
"signature": "123456xzcxcxcxcx..."
}