Add QS to fangraphs get_pitching_stats

[jarrett32]

Issue: https://github.com/jldbc/pybaseball/issues/50

Looks like fan graphs added QS as a stat, and maybe a few more (table rows 392-420) that we could add in the future, but this PR quickly adds QS to the end of the table

Example:

from pybaseball.pitching_leaders import pitching_stats

t = pitching_stats(2024).reset_index(drop=True)
for col in t.columns:
    print(col, t[col][0])