XPath matcher support

[denandz]

Proposed changes

This pull request adds XPath matcher support. The same libraries as used by the extractor functionality are re-used here, so we have no new dependencies. Closes #4086

The following template and output shows the new XPath matcher support:

id: title-check

info:
  name: title-check
  author: test
  severity: critical

http:
  - raw:
      - |
        GET / HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: xpath
        part: body
        xpath:
          - "/html/head/title[contains(text(), 'Example Domain')]"

:~$ nuclei -t xpath-test.yaml -u http://example.com

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v2.9.12

		projectdiscovery.io

[INF] Current nuclei version: v2.9.12 (latest)
[INF] Current nuclei-templates version: v9.6.2 (latest)
[INF] New templates added in latest release: 61
[INF] Templates loaded for current scan: 1
[INF] Targets loaded for current scan: 1
[title-check] [http] [critical] http://example.com/

The validation logic has been extended to return information about XPath syntax errors to end users, rather than just silently failing.

:~$ ./nuclei -t xpath-brokentest.yaml -validate

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v2.9.12

		projectdiscovery.io

[ERR] Error occurred parsing template /home/doi/xpath-brokentest.yaml: could not compile request: could not compile operators: could not compile matcher: /html/head/title[contains(text(), 'Example Domain'))] has an invalid token
[FTL] Could not validate templates: errors occurred during template validation

Checklist

• Pull request is created against the dev branch
• All checks passed (lint, unit/integration/regression tests etc.) with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[tarunKoyalwar]

lgtm !

Awesome Work @denandz !!!

$ go run . -u example.com -t ~/test-templates/xpath-matcher.yaml -ms              

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v2.9.12

		projectdiscovery.io

[INF] Current nuclei version: v2.9.12 (latest)
[INF] Current nuclei-templates version: v9.6.2 (latest)
[INF] New templates added in latest release: 61
[INF] Templates loaded for current scan: 1
[INF] Targets loaded for current scan: 1
[INF] Running httpx on input host
[INF] Found 1 URL from httpx
[title-check] [matched] [http] [critical] https://example.com/