Adds Export to flamegraph.com

[cyriltovena]

Now that we have CORS setup on the flamegrah.com side, we can simply call the API from here.

I also merged improvement to use saveAs library

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[simonswine]

LGTM

I have given that a try and it works for me

[cyriltovena]

I'm adding more commit as I'm testing it in Grafana too :/