Enable dark mode automatically when the browser's user preference is set to dark mode about readder

[andreasvirkus]

🙋‍♂ I'd like to tackle this

[sleepyfran]

@andreasvirkus yeah, I remember having the same issues back when I installed the dependencies for the first time, even in Mojave. I don't remember what I did to solve them finally but right now I have node v10.16.3, so that might be the answer hahaha

As of the code it's looking great so far! I'd definitely advice to either call the CHANGE_THEME mutation directly or adding an optional parameter to the current SWITCH_THEME since this will come in handy if we finally decide to implement some kind of persistence; talking of which, I briefly mentioned it in #16, so it's definitely up to you, if you prefer you can work on this feature on its own and then add some persistence in another branch that we can reuse to start implementing the settings or do it all in this PR and we can continue from here once we decide to start working on the settings. The same for localStorage or a cookie! 😋

Thanks for the great work!

[sleepyfran]

🙋‍♂ I'd like to tackle this

@andreasvirkus great to hear! If you have any doubts or want to discuss any technical detail feel free to mention it here 😃

_{Sent with GitHawk}

[andreasvirkus]

I had a hard time getting the dependencies to install locally (on MacOS Catalina) because of some infamous node-gyp errors 😞 (with Node v12.11.1)... I might just have to downgrade my Node verson to 8.* something, as some issues under the node-gyp library suggest :/

I started working on the code nonetheless - That's what I've added so far - https://github.com/andreasvirkus/readder/blob/feature/theme-preferences/src/view/App.vue#L33-L60
(I'll most likely also add a state param to the switchTheme action instead of creating separate actions per theme? So if no param is passed in, it'll act as a toggle (current functionality))

We can use window.matchMedia to initially check for the preference as well as add a listener so it's reactive to any changes that happen while the user is on the site!

Btw, I saw that the theme choice is not persisted atm between site visits - would it be OK to save it in localStorage (or a cookie, up to you) for example? If yes, can I do it within this same issue or would you like it to be a separate PR?