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/reference-container.php

@@ -0,0 +1,78 @@
+<?php // phpcs:disable WordPress.Files.FileName.InvalidClassFileName, WordPress.Security.EscapeOutput.OutputNotEscaped
+/**
+ * Includes the Plugin Widget to put the Reference Container to the Widget area.
+ *
+ * @filesource
+ * @package footnotes
+ * @since 1.5.0
+ */
+
+/**
+ * Registers a Widget to put the Reference Container to the widget area.
+ *
+ * @since 1.5.0
+ */
+class Footnotes_Widget_Reference_Container extends Footnotes_Widget_Base {
+
+	/**
+	 * Returns an unique ID as string used for the Widget Base ID.
+	 *
+	 * @since 1.5.0
+	 * @return string
+	 */
+	protected function get_id() {
+		return 'footnotes_widget';
+	}
+
+	/**
+	 * Returns the Public name of the Widget to be displayed in the Configuration page.
+	 *
+	 * @since 1.5.0
+	 * @return string
+	 */
+	protected function get_name() {
+		return Footnotes_Config::C_STR_PLUGIN_NAME;
+	}
+
+	/**
+	 * Returns the Description of the child widget.
+	 *
+	 * @since 1.5.0
+	 * @return string
+	 *
+	 * Edit: curly quotes 2.2.0
+	 */
+	protected function get_description() {
+		return __( 'The widget defines the position of the reference container if set to “widget area”.', 'footnotes' );
+	}
+
+	/**
+	 * Outputs the Settings of the Widget.
+	 *
+	 * @since 1.5.0
+	 * @param mixed $instance The instance of the widget.
+	 * @return void
+	 *
+	 * Edit: curly quotes 2.2.0
+	 */
+	public function form( $instance ) {
+		echo __( 'The widget defines the position of the reference container if set to “widget area”.', 'footnotes' );
+	}
+
+	/**
+	 * Outputs the Content of the Widget.
+	 *
+	 * @since 1.5.0
+	 * @param mixed $args     The widget's arguments.
+	 * @param mixed $instance The instance of the widget.
+	 */
+	public function widget( $args, $instance ) {
+		global $g_obj_mci_footnotes;
+		// Reference container positioning is set to "widget area".
+		if ( 'widget' === Footnotes_Settings::instance()->get( Footnotes_Settings::C_STR_REFERENCE_CONTAINER_POSITION ) ) {
+			// phpcs:disable WordPress.Security.EscapeOutput.OutputNotEscaped
+			echo $g_obj_mci_footnotes->a_obj_task->reference_container();
+			// phpcs:enable
+		}
+	}
+}