Switch tabs by horizontal swipe

[shuuji3]

Some pages in Elk has multiple tabs and we can change between tabs by clicking them at the top of screens.

It'd be nice to be able to change to the next tab by swiping the page horizontally. This is especially handy when using Elk on mobile and it can provide more native app like experience.

This is the example of the equivalent switching feature on Andrpid app.

https://www.digitalocean.com/community/tutorials/android-viewpager-example-tutorial#:~:text=The%20image%20below%20shows%20the%20app%20in%20action.