www/chromium: add support for USB U2F devices

Implement enough of chrome.hid API to make U2F security keys work.

Due to FreeBSD's HID API limitations it's not possible to consistently
report vedor id or product id values for HID devices so if javascript
library relies on this information to detect supported keys it won't
work, only report descriptor based detection works.

Also by default uhid(4) devices accessible only to root user, current
solution is to change /dev/uhidX node permission using devd. For example
create /usr/local/etc/devd/yubi.conf with following content and
restart devd:

attach 20 {

match "vendor" "0x1050";
action "/bin/chmod 766 /dev/$device-name";

};

Work on u2f-devd port is in progress (see PR). When done it will take
care of maintaining devd rulesets for U2F devices.

PR: 196754
Approved by: cpm