Document how to see the output

[certik]

As a follow up to #27, let's document how to see the output. The README now describes to change the logging settings. However when you do that, You will not see anything by default. Here is how to see the logs:

• Open the terminal and click on the "Output" tab
• In the pop up menu, select "LFortran Language Server"

After that you will see all communication in the Output tab. Let's document the above in the README.