Support for password-protected PEM files

[paulyoung]

Both keysmith and dfx support password-protected PEM files.

Is there already a way to use a password-protected PEM file with quill?

[bitdivine]

Note: dfx also supports keychains. There might be some conflict between keeping quill as simple and secure as possible and adding support for more keys, but if the outcome of that dilemma is to support more keys, maybe the message signing agent can be extracted from dfx into a library and used here as well.