Plugins: Allow providing description

adminer/include/plugin.inc.php

@@ -1,14 +1,22 @@
 <?php
 namespace Adminer;
 
+// the overridable methods don't use return type declarations so that plugins can be compatible with PHP 5
 abstract class Plugin {
 	/** @var array<literal-string, string|list<string>>[] */ protected static $translations = array(); // key is language code
 
+	/** Get plain text plugin description; empty string means to use the first line of class doc-comment
+	* @return string
+	*/
+	function description() {
+		return '';
+	}
+
 	/** Translate a string from static::$translations; use Adminer\lang() for strings used by Adminer
 	* @param literal-string $idf
 	* @param float|string $number
 	*/
-	protected function lang(string $idf, $number = null) {
+	protected function lang(string $idf, $number = null): string {
 		$args = func_get_args();
 		$args[0] = idx(static::$translations[LANG], $idf) ?: $idf;
 		return call_user_func_array('Adminer\lang_format', $args);