<!-- Enter a brief description/summary of your PR here. What does it fix/what does it change/how was it tested (even manually, if necessary)? -->
## Summary of the Pull Request
Conhost can now support OSC8 sequences (as specified [here](https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda)). Terminal also supports those sequences and additionally hyperlinks can be opened by Ctrl+LeftClicking on them.
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## References
#204
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## PR Checklist
* [X] Closes#204
* [ ] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx
<!-- Provide a more detailed description of the PR, other things fixed or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments
Added support to:
- parse OSC8 sequences and extract URIs from them (conhost and terminal)
- add hyperlink uri data to textbuffer/screeninformation, associated with a hyperlink id (conhost and terminal)
- attach hyperlink ids to text to allow for uri extraction from the textbuffer/screeninformation (conhost and terminal)
- process ctrl+leftclick to open a hyperlink in the clicked region if present
<!-- Describe how you validated the behavior. Add automated tests wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
Open up a PowerShell tab and type
```PowerShell
${ESC}=[char]27
Write-Host "${ESC}]8;;https://github.com/microsoft/terminal${ESC}\This is a link!${ESC}]8;;${ESC}\"
```
Ctrl+LeftClick on the link correctly brings you to the terminal page on github
614507b95b
