List asdf/mise and this plugin as an install method for tkn-pac

[Barak Korren]

List asdf/mise and this plugin as an install method for tkn-pac in the official PAC docs.

Relevant PAC Docs page: https://github.com/openshift-pipelines/pipelines-as-code/blob/main/docs/content/docs/guide/cli.md

Its best if #4 is done before I try this