Update technical-overview.md

[fossette]

Fixed dead links: Android and iOs runtime overview; Plugins documentation.

PR Checklist

• [ ] The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• [ ] If there is an issue related with this PR, point it out here.

What is the current state of the documentation article?

Dead links: Android and iOs runtime overview; Plugins documentation.

What is the new state of the documentation article?

Fixed dead links: Android and iOs runtime overview; Plugins documentation.

Fixes/Implements/Closes #[Issue Number].

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