js: reorganize Javascript file structure.

Move Javascript files from app/components/**/*.js back to app/javascript/src/javascripts/*.js.
This way Javascript files are in one place, which simplifies import paths and makes it
easier to see all Javascript at once.

app/javascript/src/javascripts/comment_component.js

@@ -0,0 +1,52 @@
+import Utility from "./utility";
+
+class CommentComponent {
+  static initialize() {
+    if ($("#c-posts #a-show, #c-comments").length) {
+      $(document).on("click.danbooru.comment", ".edit_comment_link", CommentComponent.showEditForm);
+      $(document).on("click.danbooru.comment", ".expand-comment-response", CommentComponent.showNewCommentForm);
+      $(document).on("click.danbooru.comment", ".unhide-comment-link", CommentComponent.unhideComment);
+      $(document).on("click.danbooru.comment", ".comment-copy-id", CommentComponent.copyID);
+      $(document).on("click.danbooru.comment", ".comment-copy-link", CommentComponent.copyLink);
+    }
+  }
+
+  static showNewCommentForm(e) {
+    $(e.target).hide();
+    var $form = $(e.target).closest("div.new-comment").find("form");
+    $form.show();
+    $form[0].scrollIntoView(false);
+    $form.find("textarea").selectEnd();
+    e.preventDefault();
+  }
+
+  static showEditForm(e) {
+    $(this).closest(".comment").find(".edit_comment").show();
+    e.preventDefault();
+  }
+
+  static unhideComment(e) {
+    let $comment = $(this).closest(".comment");
+    $comment.find(".unhide-comment-link").hide();
+    $comment.find(".body").show();
+    e.preventDefault();
+  }
+
+  static async copyID(e) {
+    let id = $(this).closest(".comment").data("id");
+    let link = `comment #${id}`;
+    Utility.copyToClipboard(link);
+    e.preventDefault();
+  }
+
+  static async copyLink(e) {
+    let id = $(this).closest(".comment").data("id");
+    let link = `${window.location.origin}/comments/${id}`;
+    Utility.copyToClipboard(link);
+    e.preventDefault();
+  }
+}
+
+$(document).ready(CommentComponent.initialize);
+
+export default CommentComponent;