feat(design): update modal API so that the modal service can be used to close a modal with the ESC key

[xelaint]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/graycoreio/daffodil/blob/develop/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

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

What is the current behavior?

The modal is not closable via the ESC key.

Fixes:

What is the new behavior?

Does this PR introduce a breaking change?

[x] Yes
[ ] No

Breaking change: The return type of open and the argument type of close have changed. It now returns DaffModalComponent instead of DaffModal.

Other information

[damienwebdev]

lgtm