feat:✨Added support of date-time format for the groupSeparatorBuilder…

[jaiminrana05]

…(#93).

Description

Checklist

• [x] The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).
• [x] I have followed the Contributor Guide when preparing my PR.
• [ ] I have updated/added tests for ALL new/updated/fixed functionality.
• [x] I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• [x] I have updated/added relevant examples in examples or docs.

Breaking Change?

• [x] Yes, this PR is a breaking change.
• [ ] No, this PR is not a breaking change.

Related Issues

Closes #93