Replace download link with new one in doc

[crapthings]

https://github.com/peggyjs/peggy/blob/main/docs/index.html#L53

            <span id="download">
                <a
                    title="Download a minified version of Peggy for the browser"
                    href="https://github.com/pegjs/pegjs/releases/download/v0.10.0/peg-0.10.0.min.js"
                >minified</a>
                |
                <a
                    title="Download Peggy for the browser"
                    href="https://github.com/pegjs/pegjs/releases/download/v0.10.0/peg-0.10.0.js"
                >development</a>
            </span>

the old release has js file with release

so where we link new peggy?

[hildjj]

I've only got a minified build handy with the current build process. Once we're done with #60, hopefully there will be a sourcemap'd version in github, which will be appropriate for development use.

[hildjj]

Adding a download attribute wouldn't cause a download because this is being served cross-site. Re-opening so this can be re-fixed after #60.

[hildjj]

This no longer depends on #60. This could just be a download link to https://peggyjs.org/vendor/peggy/peggy.min.js, but I want to make it clear that people should be caching it from unpkg rather than github.