Support Query readPreference

[dplewis]

See parse-community/parse-server#5515

[codecov]

Codecov Report

Merging #446 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #446      +/-   ##
============================================
+ Coverage     96.95%   96.97%   +0.02%     
- Complexity     1048     1055       +7     
============================================
  Files            39       39              
  Lines          2920     2940      +20     
============================================
+ Hits           2831     2851      +20     
  Misses           89       89

Impacted Files	Coverage Δ	Complexity Δ
src/Parse/ParseQuery.php	99.75% <100%> (+0.01%)	122 <1> (+7)	⬆️

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