Update mint-005 and Add mint-006 through mint-009

[Rob1Ham]

1. MINT-005 Updates: Minor typo fixes and improvements to the existing mint-005.md proposal
2. New Proposals: Adds four new Miniscript template proposals:
   • mint-006.md
   • mint-007.md
   • mint-008.md
   • mint-009.md

mint-006, mint-007, and mint-008 are structurally similar to mint-005, but with variations on the number of keys held by the principal (1 key or 3 keys), and order in which sovereign recovery vs the emergency recovery spend conditions occur. These small changes each result in different expected output descriptor formats.

mint-009 is a multiple agent model on how multiple key agents can hold funds on behalf of a user.