fix(cli): add timeout waiting for page to be ready

[Elte156]

Partly addresses #230

I discovered my CLI issue was because of the Content Security Policy (CSP) headers that I set in my web app.
When I set Content-Security-Policy to script-src 'unsafe-inline';, AXE is then able to process the page.

This timeout is to force AXE to fail after 10 seconds of waiting; instead of indefinitely waiting for .deque-axe-is-ready (which will never be injected because of strict CSP headers in place).

Sample output with timeout in place

Running axe-core 4.2.0 in chrome-headless

Testing http://example.com ... please wait, this may take a minute.
 
An error occurred while testing this page.
Please report the problem to: https://github.com/dequelabs/axe-cli/issues/

[michael-siek]

Thank you very much for your contribution @Elte156!

[michael-siek]

• reviewed for security

[Elte156]

No problem! @michael-siek