fix: broken links and minor typos

[avats-dev]

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• 3 dead links in https://github.com/NativeScript/docs/blob/master/docs/core-concepts/technical-overview.md #1930

What is the current state of the documentation article?

I fixed three broken links due to minor typos in the urls as mentioned in the related issue.

What is the new state of the documentation article?

Links are now working.

Fixes/Implements/Closes #1930 .

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[avats-dev]

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