use proxy config lsp server url

[zhixzhan]

Is your feature request related to a problem? Please describe.

BotFramework-Composer/Composer/packages/client/src/pages/language-generation/code-editor.tsx

Lines 25 to 27 in 1a750e5

	// lsp server port should be same with composer/server port.
	const lspServerPort = process.env.NODE_ENV === 'production' ? process.env.PORT || 3000 : 5000;
	const lspServerPath = '/lg-language-server';

Describe the solution you'd like
component should not aware those env, just always same with server url

Describe alternatives you've considered

1. For development environment, use webpack-dev-server proxy lsp websocket request to server 5000;
2. For production environment, it is current server url, nothing need to do.