better error output in case the yaml could not be parsed

[lagebaue]

For validate (or lint) actions:
Currently outputs no information to the user. Extension logs are empty. only in the developer view there is a warning and even that only contains the message, not the location/stack.

        vscode.window.showErrorMessage('Could not parse OpenAPI document as JSON or YAML!');
        console.warn(ex.message);

Maybe at least log the complete error?

            let error = new vscode.Diagnostic(range, ex.message, vscode.DiagnosticSeverity.Error);
            error.source = 'openapi-lint';
            diagnostics.push(error);

Interestingly enough for translate actions (in the code) it looks like it has better error logging. But when trying to execute them I get different errors:

mainThreadExtensionService.ts:65 [[object Object]]Cannot read property 'openapi' of undefined
$onExtensionRuntimeError @ host.ts:10
_doInvokeHandler @ rpcProtocol.ts:365
_invokeHandler @ rpcProtocol.ts:365
_receiveRequest @ rpcProtocol.ts:306
_receiveOneMessage @ rpcProtocol.ts:174
(anonymous) @ rpcProtocol.ts:105
fire @ event.ts:584
fire @ ipc.net.ts:431
_receiveMessage @ ipc.net.ts:764
(anonymous) @ ipc.net.ts:624
fire @ event.ts:584
acceptChunk @ ipc.net.ts:174
(anonymous) @ ipc.net.ts:174
t @ ipc.net.ts:900
emit @ events.js:223
addChunk @ _stream_readable.js:309
readableAddChunk @ _stream_readable.js:290
Readable.push @ _stream_readable.js:224
onStreamRead @ internal/stream_base_commons.js:181
mainThreadExtensionService.ts:66 TypeError: Cannot read property 'openapi' of undefined
	at path\.vscode\extensions\mermade.openapi-lint-1.2.0\extension.js:23:99
	at path\.vscode\extensions\mermade.openapi-lint-1.2.0\node_modules\call-me-maybe\index.js:13:28
	at processTicksAndRejections (internal/process/task_queues.js:76:11)