Introduce age for another encryption method of PGP

[kachick]

But I should keep PGP, age will alt to avoid eggs in one basket.

Motivation

This is ...

dotfiles/README.md

Lines 156 to 157 in 2f3bec8

	touch ~/.ssh/id_ed25519 && chmod 400 ~/.ssh/id_ed25519
	hx ~/.ssh/id_ed25519

However using pass will depends GPG, it does not have benefit of passphrase since #852.

Of course, adding another secret manager is a way, however bitwarden does not officially support ssh integration yet. (It have PRs)

Ref

#262
https://github.com/FiloSottile/passage
https://github.com/MarkusZoppelt/nixpkgs/blob/ce12ce87a1492b4a6da8a4b20d687f13ebfdef4c/pkgs/tools/security/passage/default.nix

[kachick]

https://github.com/gopasspw/gopass also provides age option

[kachick]

💭 setting up multiple stores in gopass is not an easy task... much errors, and I should remove garbage config in each attempt

[kachick]

https://github.com/openbao/openbao is a way

[kachick]

gopass persists the config in a gitconfig style config file, not only for the password-store convention
If I removed a store, I should also remove the entry from the config.

[kachick]

gopasspw/gopass#2163 (comment)