SGM-6973 - Clean and update typography sitewide

[gitstart-app[bot]]

This PR was created by GitStart to address the requirements from this ticket: SGM-6973. This ticket was imported from: SGM-6973

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Description:

Updates the site-wide typography according to the Figma link:

https://www.figma.com/design/o1QRtdQI0ozKq0n7ATrKlx/Marketing-DLS?node-id=8435-37157&t=O1E8a0nW4Zk4jl5Y-0

• [Sourcegraph Issue] https://github.com/sourcegraph/about/issues/6973
• [Ticket] https://clients.gitstart.com/sourcegraph/3436/tickets/SGM-6973

DEMO:

https://www.loom.com/share/908c184f87b742f096bba69e9b5fa5da?sid=48121504-c679-4a93-94c5-9b8f36def212

Test cases:

• [x] Old font families Source Sans, system fonts are removed

• [x] Update Tailwind font families to 'sans': Inter 'mono': Roboto mono 'display': Space Grotesk.

• [x] Letter spacing matches letter spacing on figma

• [x] Updated blog template type styles (H1, H2, H3) and added Callout according to the specs

Test plan:

• Added text-blog-h1, text-blog-h2, text-blog-h3, text-blog-callout in the Global.css file and used the classes in the blog page headings
• Added Font families and letter spacing are found in the tailwind.config file
• Use element inspection tool in browser to check font details

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[traceyljohnson]

Also spotted this icon seems to actually not be a proper SVG, but an SVG containing a base64 encoded PNG. Could your team inspect SVGs whenever they export from Figma, to ensure this doesn't happen again? Attaching the proper SVG to this comment. Appreciate you!

[gitstart-sourcegraph]

Extra comments

Thanks @traceyljohnson Will address these ASAP