I use a tool called "Dash.app" for Mac from Kapeli [1] (I've no affiliation with them). It allows me to download the documentation for a lot of development tools for offline consumption, these docs are called "Docsets", just to give you an idea of how many docsets it has check this link [3]. It makes also very easy to navigate and search.
You can also download a "tag" from stackoverflow which is very useful.
I know there is now alternatives for several operative systems using the same docsets [2].
I can't recommend this app enough, it is worth every penny.
[2]: https://blog.kapeli.com/dash-for-ios-android-windows-or-linu...