prevent duplicate names

src/sprite_editor.js

@@ -24,8 +24,20 @@ export class SpriteEditor {
         });
         input.addEventListener("change", async () => {
             for (const file of input.files) {
+                const rootName = file.name;
+                let fullName = file.name;
+                for (let i = 0; this.sprites.some((x) => x.name === fullName); ++i) {
+                    const extensionIdx = rootName.split("").findLastIndex((x) => x === ".");
+                    let name = rootName;
+                    let extension = "";
+                    if (extensionIdx !== -1) {
+                        name = rootName.slice(0, extensionIdx);
+                        extension = rootName.slice(extensionIdx);
+                    }
+                    fullName = `${name}-${i}${extension}`;
+                }
                 this.addSprite({
-                    name: file.name,
+                    name: fullName,
                     mime: file.type,
                     bytes: await fetch(URL.createObjectURL(file)).then((x) => x.bytes()),
                 });