Update documentation for both methods of using VSCode for JupyterHub

[sungjoon0710]

Existing documentation for local VSCode is here:
https://leap-stc.github.io/guides/vscode_remoteSSH_guide.html

Our job is to create a parent document explaining the difference between the two methods (Remote SSH from Local VSCode, Launch VSCode from JupyterHub), then include links to both the vscode_remoteSSH_guide and <new_guide_from_Sarika>

@sungjoon0710 and @sarika-debruyn are collaborating on this Issue