feat: add settings for WeekView days divider

[salahmak]

Description

In WeekView, the styling for the Divider between the week days and the week view grid is hard coded (like shown in the screenshot below):

So this PR adds a new class WeekDaysDividerSettings to control the styling for that divider, also includes a autoIndent parameter to prevent the divider from taking the entire width and indenting it to start from where the days row starts.

Result with autoIndent set to true (with some styles applied through the new settings):

Same result with autoIndent set to false:

This PR also removes the useless hardcoded border below the week days:
Before (autoIndent set to True):

After:

Checklist

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

Breaking Change?

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

Related Issues

Closes #374 and #430

[PRBaraiya]

Hi @salahmak Please solve the conflicts in this PR.

[salahmak]

@PRBaraiya Should be done