Find the block for sniper skills (starts with "//Sniper") and add this row:
4012,2240,1,0,0,0,0,0,0,0,0,0,0 //RA_WUGMASTERY#Warg Mastery#
Client side (skilltreeview.lua):
[4012] = {
{"SN_FALCONASSAULT", 381; Pos = 28, MaxLv = 5, NeedSkillList = {14, 21}},
{"SN_SHARPSHOOTING", 382; Pos = 5, MaxLv = 5, NeedSkillList = {}},
{"SN_SIGHT", 380; Pos = 26, MaxLv = 10, NeedSkillList = {7}},
{"SN_WINDWALK", 383; Pos = 12, MaxLv = 10, NeedSkillList = {}}
}
Here you have a row like this:
{"RA_WUGMASTERY", 2240; Pos = 12, MaxLv = 1, NeedSkillList = {}}
I'm not sure how to handle the "Pos" field, but it's probaly for the list display... just try a bit.