Add option to separate pie chart slices using borders (partially implement #1439 )

[osamayelk]

What kind of change does this PR introduce? (check one with "x")

• [ ] Bugfix
• [x] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Other... Please describe:

What is the current behavior? (You can also link to an open issue here) Pie chart slices are always attached to each other with no spacing between them https://github.com/swimlane/ngx-charts/issues/1439

What is the new behavior? Slices can now be separated while determining the separation color and width

Does this PR introduce a breaking change? (check one with "x")

• [ ] Yes
• [x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information: A test was added to the pie chart to validate the functionality to be working

[ddenoel]

This would be great!

[AmerAnsari]

Can we have it for an Advanced Pie Chart as well?

[papagei-ma]

Would you please merge this?! :)

[guerital]

Can we have this feature in the next release?

[gyomber95]

Nice feature, great work. When it will be released?

[mwaleed0517]

Is this getting merged? Please and can you tell me if you are going to merge it, when it would be available

[osamayelk]

This has been open for two years. I don't think the maintainers are going to merge it any time soon.