Fix capitalization of "Slack" in pre-work-template---design.md issue template

[jchue]

Fixes #7194

What changes did you make?

• Capitalized "Slack" in pre-work-template---design.md when used as a proper noun

Why did you make the changes (we will use this info to test)?

• Correctly capitalize "Slack" when it's used to refer to the app or the company in our code and content.

For Reviewers

• Use this URL to check the updated issue template: https://github.com/jchue/hackforla-website/issues/new?assignees=&labels=Complexity%3A+Prework%2C+Feature%3A+Onboarding%2FContributing.md%2C+role%3A+design%2C+size%3A+1pt&projects=&template=pre-work-template---design.md&title=Pre-work+Checklist%3A+Designer%3A+%5Breplace+brackets+with+your+name%5D

Screenshots of Proposed Changes To The Website (if any, please do not include screenshots of code changes)

• No visual changes to the website

[github-actions]

Want to review this pull request? Take a look at this documentation for a step by step guide!

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From your project repository, check out a new branch and test the changes.

git checkout -b jchue-capitalize-slack-7194 gh-pages
git pull https://github.com/jchue/hackforla-website.git capitalize-slack-7194

[codyyjxn]

@jchue Thank you for taking on this issue. The branch name is correct and the commits are correct. The link provided is good I was able to see the changes you made. Good Job!

[FamousHero]

Hi @jchue thanks for taking up this issue!

• Issue number correctly referenced in branch & PR
• Descriptive PR title & changes made
• Why you made the changes is clear
• Link to updated template works well
• Followed Action Items to a tee
  Excellent work!! Keep it up!!