Index JSON (#249)

This will expose a JSON endpoint with all the pages and some meta.

It would allow us to, for example, filter posts by `tag` and maybe link to them from our main docs.

e.g. a follow-up PR to tag any "feature preview"-style posts and then link to them from our docs.

Reviewed-on: https://gitea.com/gitea/blog/pulls/249
Reviewed-by: delvh <dev.lh@web.de>
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: jolheiser <john.olheiser@gmail.com>
Co-committed-by: jolheiser <john.olheiser@gmail.com>

config.yaml

@@ -19,6 +19,12 @@ params:
   author: Gitea
   website: https://blog.gitea.io
 
+outputs:
+  home:
+    - HTML
+    - RSS
+    - JSON
+
 menu:
   page:
     - name: Website

layouts/index.json

@@ -0,0 +1,5 @@
+{{- $.Scratch.Add "index" slice -}}
+{{- range .Site.RegularPages -}}
+{{- $.Scratch.Add "index" (dict "title" .Title "tags" .Params.tags "contents" .Plain "permalink" .Permalink) -}}
+{{- end -}}
+{{- $.Scratch.Get "index" | jsonify -}}