Allow different HardBreaks settings for documents and comments (#11515)

GH has different HardBreaks behaviour for markdown comments and documents.

Comments have hard breaks and documents have soft breaks - therefore Gitea's rendering will always be different from GH's if we only provide one setting.

Here we split the setting in to two - one for documents and one for comments and other things.

Signed-off-by: Andrew Thornton art27@cantab.net

Changes to index.js as per @silverwind 
Co-authored-by: silverwind <me@silverwind.io>

Changes to docs as per @guillep2k 
Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>

web_src/js/index.js

@@ -41,7 +41,7 @@ function initCommentPreviewTab($form) {
     const $this = $(this);
     $.post($this.data('url'), {
       _csrf: csrf,
-      mode: 'gfm',
+      mode: 'comment',
       context: $this.data('context'),
       text: $form.find(`.tab[data-tab="${$tabMenu.data('write')}"] textarea`).val()
     }, (data) => {
@@ -65,6 +65,7 @@ function initEditPreviewTab($form) {
     $previewTab.on('click', function () {
       const $this = $(this);
       let context = `${$this.data('context')}/`;
+      const mode = $this.data('markdown-mode') || 'comment';
       const treePathEl = $form.find('input#tree_path');
       if (treePathEl.length > 0) {
         context += treePathEl.val();
@@ -72,7 +73,7 @@ function initEditPreviewTab($form) {
       context = context.substring(0, context.lastIndexOf('/'));
       $.post($this.data('url'), {
         _csrf: csrf,
-        mode: 'gfm',
+        mode,
         context,
         text: $form.find(`.tab[data-tab="${$tabMenu.data('write')}"] textarea`).val()
       }, (data) => {