ui: table - add "expandable" rows

[SuperITMan]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[X] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#got-a-question-or-problem

Current behavior

Elements in Stark Table component cannot have child elements.

Expected behavior

Stark Table should provide the ability to have expandable rows.

What is the motivation / use case for changing the behavior?

Improvement

Other

Some links that could help us to implement this nice feature:

• Expandable Rows in Mat-Table
• StackOverFlow discussion about expandable table rows
• Basic implementation of expanded rows on StackBlitz
• A little bit more advanced implementation of expanded rows on StackBlitz
• Angular Material Table (mat-sort-header + expandable rows) angular/components#11990

[SuperITMan]

A first implementation has been done by @nicanac and is available on nicanac@be88f90