Recover missing web tool screenshot in README.md

[microbit-grace]

Recover missing image is a screenshot of the Web tool page

Fixes #45

[microbit-carlos]

It makes the README easier to read and it clearly shows it's not just a library and that it also includes the online tools.
Is there a reason not to include the screenshot? Would it get deleted automatically every time the docs are re-generated? If that's the case, do we need to do something to make sure the minified js file doesn't get deleted again?

[microbit-grace]

It makes the README easier to read and it clearly shows it's not just a library and that it also includes the online tools. Is there a reason not to include the screenshot? Would it get deleted automatically every time the docs are re-generated? If that's the case, do we need to do something to make sure the minified js file doesn't get deleted again?

If you think strongly about including the image, I can add it back. I just thought that the text seemed sufficient in saying what the image says

[microbit-carlos]

If there isn't a reason not to include (and there could be plenty!) I would prefer to keep it, yes.

[microbit-grace]

@microbit-carlos Have recovered the missing image in the latest two commits

[microbit-carlos]

Awesome, thanks Grace!