Add option to embed the stylesheet

[jessedijkstra]

Instead of compiling the stylesheets into view by default it's now an option. This decreases the initial and recompile compile time of views when developing the application and saving CSS files:

Compiling lib/myapp_web/views/course/index/view.ex (it's taking more than 10s)
Compiling lib/myapp_web/controllers/registration_controller.ex (it's taking more than 10s)
Compiling lib/myapp_web/cells/badge/view.ex (it's taking more than 10s)
Compiling lib/myapp_web/cells/departments/employee_list/view.ex (it's taking more than 10s)
Compiling lib/myapp_web/cells/navigation/main_desktop/view.ex (it's taking more than 10s)
Compiling lib/myapp_web/views/user/edit/view.ex (it's taking more than 10s)
Compiling lib/myapp_web/views/position/show/view.ex (it's taking more than 10s)

[codecov-io]

Codecov Report

Merging #5 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master     #5   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           1      2    +1     
  Lines          19     24    +5     
=====================================
+ Hits           19     24    +5

Impacted Files	Coverage Δ
lib/ex_css_modules/view.ex	100% <100%> (ø)
lib/ex_css_modules/ex_css_modules.ex	100% <100%> (ø)	⬆️

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