Add a precompilation workload

[Tortar]

This cuts down the precompilation time quite a bit:

before:

julia> using SumTypes

julia> @time @eval @sum_type Re begin
           Empty
           Class(::UInt8)
           Rep(::Re)
           Alt(::Re,  ::Re)
           Cat(::Re,  ::Re)
           Diff(::Re, ::Re)
           And(::Re,  ::Re)
       end;
  1.448841 seconds (2.26 M allocations: 152.786 MiB, 3.72% gc time, 98.11% compilation time)

after:

julia> using SumTypes

julia> @time @eval @sum_type Re begin
           Empty
           Class(::UInt8)
           Rep(::Re)
           Alt(::Re,  ::Re)
           Cat(::Re,  ::Re)
           Diff(::Re, ::Re)
           And(::Re,  ::Re)
       end;
  0.142083 seconds (41.50 k allocations: 2.622 MiB, 82.27% compilation time)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2934ed2) 100.00% compared to head (ebce857) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #74   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         4    +1     
  Lines          265       275   +10     
=========================================
+ Hits           265       275   +10     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[MasonProtter]

Awesome stuff @Tortar!