Create vault architecture documentation

Big Bang packages require architecture documentation. Create one for vault in https://repo1.dso.mil/platform-one/big-bang/bigbang/-/tree/master/docs/understanding-bigbang/package-architecture

Ensure that HA section is present, includes information and links to package production-ha.md document: https://repo1.dso.mil/platform-one/big-bang/apps/sandbox/vault/-/blob/main/docs/production-ha.md#high-availability