fix: vertical alignment of event sidebar

[thisislawatts]

Fixing an issue with the vertical spacing above the TBD title. The first image shows the current appearance, which can be verified at: https://devopsdays.org/about

The second image shows the result of the changes, with a unit of vertical spacing introduced above the TBD heading.

The primary changes in this PR are:

• Removing the use of <br/> element for vertical spacing
• Use CSS to manage the vertical space, through a mixture of custom CSS and bootstrap utility classes.

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[github-actions]

en_US: Hi @thisislawatts! It looks like you've left the default text in the pull request description. Please replace that text with something meaningful. Thanks!
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