Add back the can-load file

modules/database/sqlite/can-load.php

@@ -0,0 +1,37 @@
+<?php
+/**
+ * Can load function to determine if SQLite can be activated.
+ *
+ * @since 1.8.0
+ * @package performance-lab
+ */
+
+/**
+ * Checks whether the given module can be activated.
+ *
+ * @since 1.8.0
+ */
+return function() {
+
+	// If the PERFLAB_SQLITE_DB_DROPIN_VERSION  or SQLITE_DB_DROPIN_VERSION constants
+	// are defined, then the module is already active.
+	if ( defined( 'PERFLAB_SQLITE_DB_DROPIN_VERSION' ) || defined( 'SQLITE_DB_DROPIN_VERSION' ) ) {
+		return true;
+	}
+
+	// If a db.php file already exists in the wp-content directory, then the module cannot be activated.
+	if ( file_exists( WP_CONTENT_DIR . '/db.php' ) ) {
+		return false;
+	}
+
+	// If the SQLite3 class does not exist, then the module cannot be activated.
+	if ( ! class_exists( 'SQLite3' ) ) {
+		return false;
+	}
+
+	// If the db.php file can't be written to the wp-content directory, then the module cannot be activated.
+	if ( ! wp_is_writable( WP_CONTENT_DIR ) ) {
+		return false;
+	}
+	return true;
+};