Add guard for Intl.Segmenter in line-text.ts, Fixes #159

[ArjunSrivastava1]

Fixes #159

• Adds a runtime guard that throws an error message when Intl.Segmenter is unavailable, preventing from finding the issue deep in a render stack somewhere.
• The error also consists of the site which lets the developers check if they are able to run the segmenter or not.
• Further, this fix includes a comment that also mentions the reqs so code and explains so its clearer.

It was deemed unecessary to add the same in the readme as it felt bloated so that wasnt done

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