Mobile Safari seems to be the only browser that does *not* resize the
viewport when the keyboard shows and hides. Instead the window is moved
to make room for the keyboard which moves content at the top off screen.
This uses the VisualViewport API to manually resize the `SessionView`
in response to keyboard display events. Additionally, if a DOM element
exists that has the `bottom-aligned-scroll` CSS class, its scroll
position is retained. Currently this only applies to the `Timeline`.
Note that the VisualViewport API was only introduced with iOS 13.
According to [statista.com], versions below 13 made up for 19% of
all iOS users in summer 2020, with the share continuing to fall off.
As a result, this seems like an acceptable workaround.
Fixes: #181
[statista.com]: https://www.statista.com/statistics/565270/apple-devices-ios-version-share-worldwide/
Signed-off-by: Johannes Marbach <n0-0ne+github@mailbox.org>
