Add email address callback

[csandr]

No description provided.

[codecov]

Codecov Report

Merging #836 into master will decrease coverage by 0.02%.
The diff coverage is 7.69%.

@@            Coverage Diff             @@
##           master     #836      +/-   ##
==========================================
- Coverage   22.77%   22.75%   -0.03%     
==========================================
  Files          95       95              
  Lines        9330     9343      +13     
  Branches      780      780              
==========================================
+ Hits         2125     2126       +1     
- Misses       7071     7083      +12     
  Partials      134      134              

Impacted Files	Coverage Δ
...t2/SteamKit2/Steam/Handlers/SteamUser/Callbacks.cs	2.77% <0.00%> (-0.12%)	⬇️
...t2/SteamKit2/Steam/Handlers/SteamUser/SteamUser.cs	25.40% <16.66%> (-0.22%)	⬇️

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[yaakov-h]

Why not expose the other fields on the message as well?