Add link to Vue Performance Devtools

[scheinercc]

Fixes #23

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[housseindjirdeh]

Thanks a million for this. When you get around to signing the CLA, will we'll land this in 💃

[scheinercc]

@housseindjirdeh - as there is no simple "yes I agree" (like e.g. for mozilla), but address and everything, do you mind doing me the favour and just copy my change over and push it for me? Then we can close this pull request I guess. Thanks in advance :)

[housseindjirdeh]

Will be pushing a PR with a few tools, will add this in there