Two new tools added to the Level Editor:
* Pan Tool: left-click to scroll the level around safely.
* Text Tool: write text onto your level.
Features of the Text Tool:
* Can choose from the game's built-in fonts, size and enter the message
you want to write.
* The mouse cursor previews the text when hovered over the level.
* Click to "stamp" the text onto your level. The currently selected
color swatch will be used to color the text in.
* Adds two new fonts: Azulian.ttf and Rive.ttf that can be selected in
the Text Tool.
Some implementation notes:
* Added package native/engine_sdl.go that handles the lower-level
SDL2_TTF logic to rasterize the text into a black&white image.
* WASM not supported yet (if the game even still built for WASM);
native/engine_wasm.go stubs out the TextToImage() call with a "not
supported" error just in case.
Other changes:
* New Toolbar icons: they are 24x24 instead of 32x32 to make more room
for more tools.
* The toolbar now shows two buttons per row for a more densely packed
layout. For very narrow screen widths (< 600px) the default Vertical
Toolbar layout will use one-button-per-row to not eat too much screen
real estate.
* In the Horizontal Toolbars layout there are 2 buttons per column.
* Add initial Ellipse Tool to the Editor Mode. Currently there's
something wrong with the algorithm and the ellipses have a sort of
'lemon shape' to them.
* Refactor the IterLine/IterLine2 functions to be more consistent.
IterLine used to be the raw algorithm that took a bunch of coordinate
numbers and IterLine2 took two render.Point's and was the main one
used throughout the app. Now, IterLine takes the two Points and the
raw algorithm function removed.
