Support sticky left and right axes

[Croge32]

This PR adds 2 new slots: sticky_left_axis and sticky_right_axis. These when used with a y_axis component within allow a user to specify that an axis should stick to the left or right of the graph.

Usage examples:

<:sticky_left_axis :let={graph}>
  <.y_axis :let={value} ...>{round(value)}°</.y_axis>
</:sticky_left_axis>

<:sticky_right_axis :let={graph}>
  <.y_axis :let={value}  position={:right} ...>{value}</.y_axis>
</:sticky_right_axis>

Screenshot of examples. Note that scrollbar is in the middle of the graph and axes are both visible:

[ngscheurich]

LGTM!