ci: improve release process, clean up and re-org repo, add automated minification (#143)

* ci: update scripts

* release 2.7.1

* remove tracked stylesheets

* docs: revert stable tag to 2.7.0

* chore: move Plugin source into own dir

* docs: delete info texts

These can now be found in the [project wiki][wiki].

[wiki]: https://github.com/markcheret/footnotes/wiki

* docs: tweak contributing guide

* ci: reflect new directory structure

* chore: update gitignore

* chore: reflect new dir structure

* docs: update documentation

* build(linting): add Husky hooks, Markdown linting, lint all MD files

* fix pre-push command

* fix pre-push command

* build: add stylesheet, JS minification

* ci: add linting steps

* ci: comment out CSS linting step (that's going to be a whole *thing*)

* ci: minify all JS files

* ci: call correct JS file

* chore: lint

* ci: fix PHP linting commands

* chore: increment version constant string

* ci: concat AMP stylesheets

* ci: improve build scripts

* chore: add assets dir

src/class/widgets/base.php

@@ -0,0 +1,86 @@
+<?php // phpcs:disable WordPress.Files.FileName.InvalidClassFileName
+/**
+ * Widget base.
+ *
+ * @filesource
+ * @package footnotes
+ * @since 1.5.0
+ *
+ * @since 1.6.4  Update: replace deprecated function WP_Widget() with recommended __construct(), thanks to @dartiss code contribution.
+ */
+
+/**
+ * Base Class for all Plugin Widgets. Registers each Widget to WordPress.
+ * The following Methods MUST be overwritten in each sub class:
+ * **public function widget($args, $instance)** -> echo the Widget Content
+ * **public function form($instance)** -> echo the Settings of the Widget
+ *
+ * @author Stefan Herndler
+ * @since 1.5.0
+ */
+abstract class Footnotes_Widget_Base extends WP_Widget {
+
+	/**
+	 * Returns an unique ID as string used for the Widget Base ID.
+	 *
+	 * @since 1.5.0
+	 * @return string
+	 */
+	abstract protected function get_id();
+
+	/**
+	 * Returns the Public name of child Widget to be displayed in the Configuration page.
+	 *
+	 * @since 1.5.0
+	 * @return string
+	 */
+	abstract protected function get_name();
+
+	/**
+	 * Returns the Description of the child widget.
+	 *
+	 * @since 1.5.0
+	 * @return string
+	 */
+	abstract protected function get_description();
+
+	/**
+	 * Returns the width of the Widget. Default width is 250 pixel.
+	 *
+	 * @since 1.5.0
+	 * @return int
+	 */
+	protected function get_widget_width() {
+		return 250;
+	}
+
+	/**
+	 * Class Constructor. Registers the child Widget to WordPress.
+	 *
+	 * @since 1.5.0
+	 *
+	 * - Update: replace deprecated function WP_Widget() with recommended __construct(), thanks to @dartiss code contribution.
+	 *
+	 * @since 1.6.4
+	 * @contributor @dartiss
+	 * @link https://plugins.trac.wordpress.org/browser/footnotes/trunk/class/widgets/base.php?rev=1445720
+	 * “The called constructor method for WP_Widget in Footnotes_Widget_ReferenceContainer is deprecated since version 4.3.0! Use __construct() instead.”
+	 */
+	public function __construct() {
+		$l_arr_widget_options  = array(
+			'classname'   => __CLASS__,
+			'description' => $this->get_description(),
+		);
+		$l_arr_control_options = array(
+			'id_base' => strtolower( $this->get_id() ),
+			'width'   => $this->get_widget_width(),
+		);
+		// Registers the Widget.
+		parent::__construct(
+			strtolower( $this->get_id() ), // Unique ID for the widget, has to be lowercase.
+			$this->get_name(), // Plugin name to be displayed.
+			$l_arr_widget_options, // Optional Widget Options.
+			$l_arr_control_options // Optional Widget Control Options.
+		);
+	}
+}