add doc page to the postinstall message

administrator/language/en-GB/en-GB.plg_system_httpheaders.ini

@@ -29,7 +29,7 @@ PLG_SYSTEM_HTTPHEADERS_HSTS_SUBDOMAINS_DESC="HSTS should also be enabled <strong
 PLG_SYSTEM_HTTPHEADERS_HSTS_SUBDOMAINS="Also for subdomains"
 PLG_SYSTEM_HTTPHEADERS_POSTINSTALL_INTRODUCTION_TITLE="HTTP Security Headers"
 ; Please do not translate the names of the http headers in the following language string
-PLG_SYSTEM_HTTPHEADERS_POSTINSTALL_INTRODUCTION_BODY="Joomla! comes with a built-in plugin that handles http security headers. It helps to secure your site by setting the following headers with the default values:<br><ul><li><a href='https://scotthelme.co.uk/hardening-your-http-response-headers/#x-frame-options' target='_blank' rel='noopener noreferrer'>'X-Frame-Options: SAMEORIGIN'</a></li><li><a href='https://scotthelme.co.uk/hardening-your-http-response-headers/#x-xss-protection' target='_blank' rel='noopener noreferrer'>'X-XSS-Protection: 1; mode=block'</a></li><li><a href='https://scotthelme.co.uk/hardening-your-http-response-headers/#x-content-type-options' target='_blank' rel='noopener noreferrer'>'X-Content-Type-Options: nosniff'</a></li><li><a href='https://scotthelme.co.uk/a-new-security-header-referrer-policy/' target='_blank' rel='noopener noreferrer'>'Referrer-Policy: no-referrer-when-downgrade'</a></li></ul><br>The full list of supported headers are: <br><ul><li><a href='https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security' target='_blank' rel='noopener noreferrer'>Strict-Transport-Security</a></li><li><a href='https://en.wikipedia.org/wiki/Content_Security_Policy' target='_blank' rel='noopener noreferrer'>Content-Security-Policy</a></li><li>Content-Security-Policy-Report-Only</li><li>X-Frame-Options</li><li>X-XSS-Protection</li><li>X-Content-Type-Options</li><li>Referrer-Policy</li><li>Expect-CT</li></ul><br>These headers help your browser to protect your website from <a href='https://en.wikipedia.org/wiki/Cross-site_scripting' target='_blank' rel='noopener noreferrer'>XSS</a> and <a href='https://en.wikipedia.org/wiki/Clickjacking' target='_blank' rel='noopener noreferrer'>Clickjacking</a> attacks."
+PLG_SYSTEM_HTTPHEADERS_POSTINSTALL_INTRODUCTION_BODY="Joomla! comes with a built-in set of tools that help you to handle http security headers. It helps to secure your site by setting the following headers with the default values:<br><ul><li><a href='https://scotthelme.co.uk/hardening-your-http-response-headers/#x-frame-options' target='_blank' rel='noopener noreferrer'>'X-Frame-Options: SAMEORIGIN'</a></li><li><a href='https://scotthelme.co.uk/hardening-your-http-response-headers/#x-xss-protection' target='_blank' rel='noopener noreferrer'>'X-XSS-Protection: 1; mode=block'</a></li><li><a href='https://scotthelme.co.uk/hardening-your-http-response-headers/#x-content-type-options' target='_blank' rel='noopener noreferrer'>'X-Content-Type-Options: nosniff'</a></li><li><a href='https://scotthelme.co.uk/a-new-security-header-referrer-policy/' target='_blank' rel='noopener noreferrer'>'Referrer-Policy: no-referrer-when-downgrade'</a></li></ul><br>The full list of supported headers are: <br><ul><li><a href='https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security' target='_blank' rel='noopener noreferrer'>Strict-Transport-Security</a></li><li><a href='https://en.wikipedia.org/wiki/Content_Security_Policy' target='_blank' rel='noopener noreferrer'>Content-Security-Policy</a></li><li>Content-Security-Policy-Report-Only</li><li>X-Frame-Options</li><li>X-XSS-Protection</li><li>X-Content-Type-Options</li><li>Referrer-Policy</li><li>Expect-CT</li><li>Feature-Policy</li></ul><br>These headers help your browser to protect your website from <a href='https://en.wikipedia.org/wiki/Cross-site_scripting' target='_blank' rel='noopener noreferrer'>XSS</a> and <a href='https://en.wikipedia.org/wiki/Clickjacking' target='_blank' rel='noopener noreferrer'>Clickjacking</a> attacks.<br>You can find more details in the <a href='https://docs.joomla.org/Special:MyLanguage/J4.x:Http_Header_Management' target='_blank' rel='noopener noreferrer'>HTTP Header Management Tutorial in the Joomla! Documentation.</a>"
 PLG_SYSTEM_HTTPHEADERS_POSTINSTALL_INTRODUCTION_ACTION="Enable default security headers"
 ; Please do not translate the following 3 language strings
 PLG_SYSTEM_HTTPHEADERS_REFERRERPOLICY="<a href='https://scotthelme.co.uk/a-new-security-header-referrer-policy/' target='_blank' rel='noopener noreferrer'>Referrer-Policy</a>"