Add Clear Site Data header

[augbog]

Show browser support for Clear Site Data header as specified in the W3C spec:
https://w3c.github.io/webappsec-clear-site-data/

It looks like a few places have already started implementing or supporting this but it isn't very clear what the status of browser support is? Related links:

https://bugs.chromium.org/p/chromium/issues/detail?id=607897
https://bugzilla.mozilla.org/show_bug.cgi?id=1268889

[mkurz]

+1

[CracyD]

+1

[Schweinepriester]

+1

• https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases/63

  The Clear-Site-Data header is implemented and no longer behind a preference (bug 1470111).

• https://www.chromestatus.com/feature/4713262029471744:
  Chrome 61+, Opera 48+
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Clear-Site-Data

EDIT, 2018-12-11:

• https://scotthelme.co.uk/a-new-security-header-clear-site-data/

[conanite]

+1

[redeye86]

+1

[Flimm]

+1

[augbog]

PR merged behind flag I think only outstanding work is maybe tests :) gonna go ahead and close.