Add support for increasing progress bar

[trevor-hackett]

This add support for the increasing progress bar requested in #192

I'm not dead set on the new config property name. Any and all feedback is welcome.

[codecov]

Codecov Report

Merging #196 into master will decrease coverage by 0.37%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master     #196      +/-   ##
==========================================
- Coverage   79.45%   79.07%   -0.38%     
==========================================
  Files          22       22              
  Lines         516      521       +5     
  Branches       65       67       +2     
==========================================
+ Hits          410      412       +2     
- Misses         57       59       +2     
- Partials       49       50       +1

Impacted Files	Coverage Δ
src/lib/toastr/toastr-config.ts	90.47% <ø> (ø)	⬆️
src/lib/toastr/default-config.ts	100% <100%> (ø)	⬆️
src/lib/toastr/toast-component.ts	77.21% <20%> (-4.12%)	⬇️
src/lib/toastr/toastr-service.ts	58.65% <0%> (+0.96%)	⬆️

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[scttcper]

sweet 🎉