Allow to set src and children in Avatar

[lcswillems]

• I have searched the issues of this repository and believe that this is not a duplicate.

Motivation 🔦

I would like to implement the avatar upload button in this Google Account page:

For this, the easiest solution (for me and for Google engineers) would be to put the upload button in the children and to show it over, i.e. to do something like this:

<Avatar src={myAvatarUrl}><UploadIcon /></Avatar>

But it doesn't work because when src is set, the children are not taken into account.

Summary

I propose to do a PR to replace the if/else at this position by:

children = childrenProp;

if (img) {
  children = (
    <>
      <img
        alt={alt}
        src={src}
        srcSet={srcSet}
        sizes={sizes}
        className={classes.img}
        {...imgProps}
      />
      {children}
    </>
  );
}

[oliviertassinari]

@lcswillems The proposal sounds good to me. I don't see any harm in it.

[lcswillems]

Great! I have just submitted a PR