adds a `CosmicCanvas` component to hold the image cosmic draws to. allows easier interop between UI and Sprite widgets

Each type of widget now uses a single `CosmicEditBundle`, adding widget specific components with `.insert()` or as tuples.

* first draft

* refine placeholder logic

bug: inputting and deleting a char on a widget quickly (i think at cursor blink speed) hold the input visually for that blink duration.

needs testing: placeholder specific attrs

* fix conflict with #73

* update placeholder attrs

* small fixes

* fix cursor showing on empty readonly widgets

---------

Co-authored-by: StaffEngineer <velo.app1@gmail.com>

* rewrite `draw_pixel`

causes overlayed text to appear correctly blended

Breaking Changes:
 - CosmicEdit*Bundle::background_color renamed to fill_color, and takes a new `FillColor(pub Color)`

* fix clippy

* Add text position Left

* Support infinite-line mode

* update readme

* update default mode name

* Add auto-height mode, refactoring

* Clippy

* Add text position Left

* Support infinite-line mode

* update readme

* update default mode name

should allow a user to install and use the plugin without needing their own install of cosmic-text

the violet color changed slightly when i set all the colors to bevy colors >.<

make edit history private; need less re-exports if this is just automagically added

removes CosmicEditor::set_text in favor of a set_text CosmicText component