do not track feature for mobile

[Jeppie]

Add this desktop feature to mobile.

https://support.mozilla.org/kb/how-do-i-turn-do-not-track-feature

[Jon]

Thanks for submitting an idea to the Mozilla Connect community! Your idea is now open to votes (aka kudos) and comments.

[luis123456789]

Does this have any good use? DNT is a well-known, documented privacy and security antipattern as sites are absolutely free to ignore the request, and actually use the data point of whether an user has DNT activated or not to feed extra data to their user tracking systems.