updated browsers that support U2F

docs/u_e-mailcow_ui-tfa.md

@@ -1,4 +1,4 @@
-So far three methods for *Two-Factor Authentication* are implemented: U2F, Yubi OTP, and TOTP
+So far three methods for _Two-Factor Authentication_ are implemented: U2F, Yubi OTP, and TOTP
 
 -   For U2F to work, you need an encrypted connection to the server (HTTPS) as well as a FIDO security key.
 -   Both U2F and Yubi OTP work well with the fantastic [Yubikey](https://www.yubico.com).
@@ -19,6 +19,23 @@ The API ID, API key and the first 12 characters (your YubiKeys ID in modhex) are
 
 ### U2F
 
+To use U2F, the browser must support this standard.
+
+The following desktop browsers support this authentication type:
+
+-   Edge (>=79)
+-   Firefox (>=47, enabled by default since version 67)
+-   Chrome (>=41)
+-   Safari (>=13)
+-   Opera (40, >=42, not 41)
+
+The following mobile browsers support this authentication type:
+
+-   Safari on iOS (>=13.3)
+-   Firefox on Android (>=68)
+
+Sources: [caniuse.com](https://caniuse.com/u2f), [blog.mozilla.org](https://blog.mozilla.org/security/2019/08/05/web-authentication-in-firefox-for-android/)
+
 Only Google Chrome (+derivatives) and Opera support U2F authentication to this day natively.
 Since version 67 Mozilla Firefox can handle U2F natively. ([Source](https://support.yubico.com/support/solutions/articles/15000017511-enabling-u2f-support-in-mozilla-firefox))