Long READMEs cause extreme lag in repository About tab

[Fs00]

I've seen that READMEs bigger than 50/60kB (like the one from this repo) cause extreme scrolling lag when previewed in the About tab of the repository screen. This becomes worse when those big READMEs contains images, since the whole text gets reflowed every time an image is downloaded and rendered (this one is an extreme example). In those cases, the app might not respond to inputs for a few seconds (even 5-10 seconds on my mid/low range phone).

To avoid these scenarios, if the README is bigger than a certain size, the app could display a notice saying something like "The README is too big to be previewed here" and maybe provide a link to open the README in the WebView-powered viewer.

[RoinujNosde]

GitHub's app doesn't seem to have this issue.