Integrate RichTextDisplay into PostingCard component

[sherryhli]

Ticket link

N/A, just spotted a use of richtext that we missed.

Implementation description

• Wrapped posting description in RichTextDisplay component

Steps to test

1. Run the application with seed data
2. Navigate to localhost:3000/volunteer/postings
3. Verify that the posting description is properly formatted (not JSON string)

4. Check the truncate behaviour (max 2 lines of description displayed in card). Create a temporary rich text string in PostingCard.tsx and pass into RichTextDisplay

const richTextSample = '{"blocks":[{"key":"2ggjh","text":"hi","type":"ordered-list-item","depth":0,"inlineStyleRanges":[],"entityRanges":[],"data":{}},{"key":"2nlb2","text":"aewf","type":"ordered-list-item","depth":0,"inlineStyleRanges":[{"offset":0,"length":4,"style":"BOLD"}],"entityRanges":[],"data":{}},{"key":"6a81d","text":"asf","type":"ordered-list-item","depth":0,"inlineStyleRanges":[{"offset":0,"length":3,"style":"BOLD"},{"offset":0,"length":3,"style":"UNDERLINE"}],"entityRanges":[],"data":{}}],"entityMap":{}}'

The full description contains 3 lines, verify that only 2 are displayed.

Side note: Chakra apparently limits the width of the second line to be less than or equal to the length of the first. @JoshuaYe @uwblueprint/sistering-w22-design is this an issue? For the example below, the second line consists of "2. aewf" but only "2. ae..." is displayed due to the first line being "1. hi".

What should reviewers focus on?

• Does it work?

Checklist

• My PR name is descriptive and in imperative tense
• My commit messages are descriptive and in imperative tense. My commits are atomic and trivial commits are squashed or fixup'd into non-trivial commits
• I have run the appropriate linter(s)
• I have requested a review from the PL, as well as other devs who have background knowledge on this PR or who will be building on top of this PR

[github-actions]

Visit the preview URL for this PR (updated for commit 025a9ec):

https://sistering-dev--pr243-sherry-posting-card-e0d2tg0s.web.app

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