Update README to say png is supported earlier

Author: kentmw

README.md

@@ -1,5 +1,5 @@
 # jpeg-web-worker
-Generate a jpeg using a web worker
+Generate a jpeg (or png) using a web worker
 
 ## Motivation
 The browser can generate a jpeg for you from an HTML canvas:
@@ -117,4 +117,4 @@ ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-The original license information about the encoder including the original port to javascript by  Andreas Ritter, and the adobe license can be found [on the jpeg-js's readme](https://github.com/eugeneware/jpeg-js#encoding)
+The original license information about the encoder including the original port to javascript by  Andreas Ritter, and the adobe license can be found [on the jpeg-js's readme](https://github.com/eugeneware/jpeg-js#encoding)