Timeline: restore the selected timeline at the next startup

[mofmofmofneko]

Closes: #581

[Dimillian]

I understand the feature request, but I might do it in a more safe way. Right now encoding the title could lead to many problem down the line. Better make the enum itself Codable so we could encode the whole filter and just re init it. RawRepresentable probably need to be extended to fit an enum or a Codable in it.

[mofmofmofneko]

Thank you for your advice. I agree with your opinion and will revise it later.

[Dimillian]

Closing it for now, I've made the timeline filter even more complexe, and this create a lot of side effects / issues. Will think about how to save / restore it correctly.