Hide column issue count

[nknguyenhc]

Summary:

Fixes #343

Type of change:

• ✨ New Feature/ Enhancement

Changes Made:

• Make each card a vertical flex box
• Shift the scrolling from .scrollable-container to .scrollable-container-wrapper
• Make the .scrollable-container-wrapper to flex grow.

Screenshots:

Proposed Commit Message:

Hide column issue count

We hide the issue column count when there is only one page,
to make space for the issues.

Checklist:

• I have tested my changes thoroughly.
• I have created tests for any new code files created in this PR or provided a link to a issue/PR that addresses this.
• I have added or modified code comments to improve code readability where necessary.
• I have updated the project's documentation as necessary.

[NereusWB922]

LGTM

[damithc]

@nknguyenhc my expectation was:

Separately, feels like showing items per page in every column (even when there are multiple pages) is redundant (and hard to use as well). Not sure how to solve it though.