feat(typeahead): add feature to do multiple search w/ specified delimiter

[lehetap]

feature allows to show typeahead dropdown even after any value
already entered by typing one of provided delimiters to be able to pick
again; keeps all searched values, described in #5781

Closes #5781

PR Checklist

Before creating new PR, please take a look at checklist below to make sure that you've done everything that needs to be done before we can merge it.

• read and followed the CONTRIBUTING.md guide.
• built and tested the changes locally.
• added/updated tests.
• added/updated API documentation.
• added/updated demos.

[lehetap]

@valorkin @daniloff200 Please review this feature as soon as possible. I added demo, tests, all that required. I desperately need it in my project.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (development@539dc28). Click here to learn what that means.
The diff coverage is 82.92%.

@@              Coverage Diff               @@
##             development    #5784   +/-   ##
==============================================
  Coverage               ?   73.75%           
==============================================
  Files                  ?      323           
  Lines                  ?    11689           
  Branches               ?     2487           
==============================================
  Hits                   ?     8621           
  Misses                 ?     1961           
  Partials               ?     1107           

Impacted Files	Coverage Δ
demo/src/ng-api-doc.ts	100.00% <ø> (ø)
src/typeahead/typeahead-utils.ts	83.33% <73.33%> (ø)
src/typeahead/typeahead.directive.ts	80.65% <88.46%> (ø)
src/timepicker/timepicker.module.ts	78.94% <0.00%> (ø)
src/accordion/accordion.module.ts	78.94% <0.00%> (ø)
src/tabs/tab.directive.ts	94.02% <0.00%> (ø)
...mes/bs/bs-datepicker-inline-container.component.ts	72.22% <0.00%> (ø)
src/tabs/tabset.config.ts	69.23% <0.00%> (ø)
src/chronos/utils/start-end-of.ts	100.00% <0.00%> (ø)
src/datepicker/bs-daterangepicker-inline.config.ts	70.37% <0.00%> (ø)
... and 316 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 539dc28...84cc259. Read the comment docs.

[daniloff200]

hey, @lehetap
Thank you for your contribution!
I was a little bit busy with some other fix requests, also, there were bunch of issues, related to 6.0.0 . I will check this PR during this week

[daniloff200]

Well, I've checked that feature, looks really awesome!
Also, looks like all other things works exactly in the same way, and nothing was broken, so, gonna merge that
It will be available in 6.0.1 release

Gonna check units and e2e's and, if everything works well, merge that

[lehetap]

Thank you! I'm glad everything worked out well!