update to exception handling ddoc in c++ interop

[Emmankoko]

this is a PR to update the state of the C++ interoperability with the exception handling in D. it's not a complete PR yet for review. will ping you guys for review when ready.

[dlang-bot]

Thanks for your pull request and interest in making D better, @Emmankoko! We are looking forward to reviewing it, and you should be hearing from a maintainer soon. Please verify that your PR follows this checklist:

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