feat: Add generic for payload in IndividualConfig

[twittwer]

relates #904

Add generic to payload in IndividualConfig to enable stricter typing.

[codecov]

Codecov Report

Patch coverage: 28.57% and project coverage change: +0.39 🎉

Comparison is base (efaf809) 55.11% compared to head (9b88f9e) 55.51%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #980      +/-   ##
==========================================
+ Coverage   55.11%   55.51%   +0.39%     
==========================================
  Files          19       19              
  Lines         508      508              
  Branches       88       88              
==========================================
+ Hits          280      282       +2     
  Misses        216      216              
+ Partials       12       10       -2     

Impacted Files	Coverage Δ
src/lib/toastr/toastr.service.ts	51.04% <0.00%> (+2.08%)	⬆️
src/lib/toastr/toast.component.ts	73.95% <100.00%> (ø)
src/lib/toastr/toastr-config.ts	94.73% <100.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[scttcper]

🎉 This PR is included in version 16.1.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀