extension and vscode lockdown in example post request

[yilmazdurmaz]

this may or may not be related to #119

the following example code causes one process use full cpu core, notebook tab locks so cannot be closed, nor vscode is able to close itself because saving notebook takes like forever

GET https://www.google.com
    ?query="fun"
    &page=2
User-Agent: rest-book
Content-Type: application/json 

[sapeurfaire]

Can confirm that setting User-Agent is problematic. (I spent a bit trying to make a patch per #119 but couldn't figure out how to build the extension. Apologies.)