fix: typo in title of welcome slideshow

[bertday]

Description

Thank you for all your hard work on the awesome devtools!

This is a minor edit to fix a typo in the title of the welcome slide show. This is missing an "a" before "little tour". Also, I would say it's more common (in American English, at least) to say "take a tour" vs. "have a tour", though they may both be correct.

Additional context

n/a

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[Akryum]

Thanks!