fix: Change function to return File instead of Blob

[KantaHasegawa]

Why

According to index.d.ts, the imageCompression(compress) function is expected to return a File object.

browser-image-compression/lib/index.d.ts

Line 32 in d933bc8

declare function imageCompression(image: File, options: Options): Promise<File>;

However, it currently returns a Blob object rather than a File.

This Blob is not a pure Blob type, but a custom Blob type that has been extended with the name and lastModified properties.

In TypeScript's built-in type definitions, a Blob type object that has the lastModified and name properties is considered a File type. This is indicated in the lib.dom.d.ts file of TypeScript:

typescript/lib/lib.dom.d.ts

/** Provides information about files and allows JavaScript in a web page to access their content. */
interface File extends Blob {
    readonly lastModified: number;
    readonly name: string;
}

Therefore, since the Blob returned by this function has the lastModified and name properties, it can be safely converted to a File type without issues.

What I Did

I have updated the return types of the following three functions from Blob to File:

imageCompression(compress)
getFilefromDataUrl
canvasToFile

before

after

[KantaHasegawa]

cc.
@Donaldcwl