Show notification when certificate verification fails

> Currently the user would have to add any custom certificate in both places to get consistent behavior. Its bit difficult to solve this, since node doesn't care about NSS db we will write our own native module which would essentially be a wrapper around https://source.chromium.org/chromium/chromium/src/+/master:net/cert/nss_cert_database.h to allow importing client certificates to the shared NSS db. I think we can better surface the error with a notification `net::ERR_CERT_AUTHORITY_INVALID` using https://github.com/electron/electron/blob/master/docs/api/app.md#event-certificate-error and ask users to add certificate in the NSS db with https://chromium.googlesource.com/chromium/src/+/lkgr/docs/linux/cert_management.md#add-a-certificate _Originally posted by @deepak1556 in https://github.com/microsoft/vscode/issues/93595#issuecomment-615018175_