Install instructions from docs

Fixes #20

Author: philwareham

src/templates/pages/plugins.txp

@@ -374,27 +374,13 @@ if (!empty($json->legacy)) {
                                 </txp:php>
                             </dl>
                         </txp:if_variable>
-                        <txp:evaluate>
+                        <txp:evaluate test>
                             <h3 id="installation">Installation instructions</h3>
                             <txp:if_variable name="txt-plugin">
-                                <h4>How to install a TXT-format plugin (Textpattern CMS 4.7 onwards)</h4>
-                                <ol>
-                                    <li>Download the TXT file.</li>
-                                    <li>Navigate to the ‘Plugins’ panel in Textpattern.</li>
-                                    <li>Select and upload the plugin using the ‘Upload plugin’ file uploader.</li>
-                                    <li>Select the ‘Install’ button on the verify plugin page to finish the installation and add the plugin to the plugin list table.</li>
-                                    <li>When ready, activate the plugin in the ‘Active’ column in the plugin list table.</li>
-                                </ol>
+                                <p><a target="_blank" href="https://docs.textpattern.com/build/plugins-installing-upgrading-and-using#a-text-txt-file">How to install a TXT format plugin</a></p>
                             </txp:if_variable>
                             <txp:if_variable name="php-plugin">
-                                <h4>How to install a PHP-format Textpattern plugin (Textpattern CMS 4.7 onwards)</h4>
-                                <ol>
-                                    <li>Download the PHP archive and unzip the contents.</li>
-                                    <li>Move the unzipped folder into your designated Textpattern <code>plugins</code> directory.</li>
-                                    <li>Navigate to the ‘Plugins’ panel in Textpattern.</li>
-                                    <li>Select and import the plugin using the ‘Import from disk’ selector.</li>
-                                    <li>When ready, activate the plugin in the ‘Active’ column in the plugin list table.</li>
-                                </ol>
+                                <p><a target="_blank" href="https://docs.textpattern.com/build/plugins-installing-upgrading-and-using#a-zip-zip-package">How to install a PHP <code>.zip</code> format plugin</a></p>
                             </txp:if_variable>
                         </txp:evaluate>
                         <p class="alert-block information footnote report-issues">If you notice any kind of problem with this page’s construction or content (plugin doesn’t work as stated, outdated information, typos, broken links, or whatever), <a rel="external" target="_blank" href="https://github.com/textpattern/textpattern-curated-plugins-list/issues/new/choose">open an issue</a> and we’ll investigate.</p>