Add a configuration option to disable emptying of the output directory

[caendesilva]

No description provided.

[codecov]

Codecov Report

Merging #136 (f3d0ce3) into master (8aa2ecd) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master     #136   +/-   ##
=========================================
  Coverage     99.23%   99.23%           
- Complexity      760      761    +1     
=========================================
  Files            97       97           
  Lines          1969     1970    +1     
=========================================
+ Hits           1954     1955    +1     
  Misses           15       15           

Impacted Files	Coverage Δ
...mework/src/Commands/HydeBuildStaticSiteCommand.php	100.00% <100.00%> (ø)

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