bevy::picking integration and refactoring (#167)

* wip: seperating cursor event handling
preparing to directly use bevy::picking instead

* mark: removed all padding and offset from render code

* bug: not rendering until focussed?

* feat: text now follows horizontal alignment

* add: example basic_sprite_editor

* feat: now centers vertically as well

* todo: get proper clicking input to work
Translating from widget to buffer coord space is annoying ngl

* feat: top_padding works correctly with click input

* refactor: moved output under render_implemetations module

* bug: for some reason, renders the same image to all editors?

* fix: editors render properly now

* mark: shift key supported in sprites

* feat: all click funcionatlity for sprites work!

* feat: primary input uses bevy::picking

* refactor: moved `RelativeCoord` into render_implementations/coords.rs

* refactor: moved `CosmicWidgetSize` into render_implementations/widget_size.rs

* refactor: Seperating input.rs into submodules

* wip: refactoring input into drag

* todo: finish hover impl

* todo: implement proper hovering

* feat: cursor hovering is well behaved!

* mark: doesn't deselect on dragend

* add: input/cursor_visbility.rs and various module refactors

* feat: focus_on_click observer

* mark: doctests all pass

* refactor: scan.rs in render_implementations and removed editor examples

* fmt

* fix: compiles on wasm now

* fix: ui clicking works now

* todo: use new EditorBuffer API

* todo: finish refactor into editor_buffer.rs module

* todo: refactor all code to use EditorBuffer

* feat: all compiles!

* todo: fix bug where cursor doesn't show on empty editors

* fix: cursor blinks in empty wdigets now

* add: veritcal scrolling only kicks in with canvas larger than render target

* fix: infinite line works

* chore: added CosmicWrap::InfiniteLine where removed before because of pancis

* chore: minor privacy restrictions

* fix: no warnings in examples