Calling Buffer constructor directly is deprecated

[caphosra]

It seems that this project uses Buffer constructor on these two lines:

vscode-jupyter/src/platform/debugger/extension/helpers/protocolParser.node.ts

Line 31 in e07a767

private rawData = new Buffer(0);

vscode-jupyter/src/webviews/extension-side/plotting/plotViewer.node.ts

Lines 145 to 148 in e07a767

	case '.png':
	const buffer = new Buffer(payload.png.replace('data:image/png;base64', ''), 'base64');
	await this.fs.writeLocalFile(file.fsPath, buffer);
	break;

According to the nodejs document, we should use Buffer.from() or Buffer.alloc() instead of new Buffer(...).
I think it would be better if we replace it.

The Buffer() and new Buffer() constructors are not recommended for use due to security and usability concerns. Please use the new Buffer.alloc(), Buffer.allocUnsafe(), or Buffer.from() construction methods instead.

Screenshot

[amunger]

Thanks for creating this - it would be great to cut down on the errors we see in the console.