Add SimplePixelArt to Vector/Image Editor and Tile/Level Editors (#490)

* Add SimplePixelArt to Vector/Image Editor and Tile/Level Editors

* Use the tileset editor URL

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Co-authored-by: Ellison <ellisonleao@gmail.com>

README.md

@@ -147,6 +147,7 @@ _Great graphics placeholders and tools to turn that squared game into a picasso
 - :tada: [Material Maker](https://github.com/RodZill4/material-maker) - procedural texture creator made in Godot
 - :tada: [OGMO Editor](https://ogmo-editor-3.github.io/)- generic level editor.
 - :tada: [Overlap2D](https://github.com/UnderwaterApps/overlap2d/) - a 2D level and UI editor with an engine agnostic philosophy.
+- :free: [SimplePixelArt Tileset Editor](https://simplepixelart.com/tilesets/editor) - Draw auto-tile tilesets in the browser and export them as Godot TileSet (.tres) and Tiled (.tsx) files.
 - :free: [Sprite Fusion](https://spritefusion.com/) - A free level design tool to craft beautiful 2D tilemaps right in your browser using any tileset.
 - :tada: [Tiled](https://www.mapeditor.org/) - free, easy to use and flexible tile map editor.
 
@@ -194,6 +195,7 @@ _Great graphics placeholders and tools to turn that squared game into a picasso
 - :moneybag: [PyxelEdit](https://pyxeledit.com/) - Pixel art editor designed to make it fun and easy to make tilesets, levels and animations.
 - :free: [REXPaint](https://www.gridsagegames.com/rexpaint/) - a powerful and user-friendly ASCII art editor.
 - :tada: [rx](https://rx.cloudhead.io/) - a modern & minimalist pixel editor
+- :free: [SimplePixelArt](https://simplepixelart.com/) - Free browser pixel art editor with layers, animation frames and palettes; exports PNG, GIF and sprite sheets with Aseprite-style frame tags for game engines.
 - :tada: [Sprite Fusion Pixel Art Cleaner](https://www.spritefusion.com/pixel-snapper) - Convert messy AI-generated pixel art into true, pixel-perfect pixel art. [Source](https://github.com/Hugo-Dz/spritefusion-pixel-snapper)
 - :free: [Spritemate](https://www.spritemate.com) - Online Editor for Commodore 64 Sprites
 - :tada: [Squoosh](https://squoosh.app) - Make images smaller using best-in-class codecs, right in the browser.