Incompatibility with Anthropics’ New Messages API

[MJE43]

Hey! So, I'm having some issues when trying to use the Claude3 models with PromptLab, it's not playing nice with the latest version of Anthropics' 'messages' API. The problem is that the new API needs an extra header, "anthropic-version", in the request. Since the extension settings doesn't include a space to specify additional headers, I can't make successful API calls.

Here's an example of what the request should look like:

curl https://api.anthropic.com/v1/messages
--header "x-api-key: $ANTHROPIC_API_KEY"
--header "anthropic-version: 2023-06-01"
--header "content-type: application/json"
--data
'{
"model": "claude-3-opus-20240229",
"max_tokens": 1024,
"messages": [
{"role": "user", "content": "Hello, world"}
]
}'

Could you please help update the extension to include this new header? Thanks a bunch in advance!