feat: add support for editing pages in Netlify CMS

Adds support for writing blog posts and editing privacy policy and terms pages.

To use,
- You must already be using Netlify to deploy your site
- Login to Netlify and setup your editors under the Identity section
- Head over to YOUR_URL/admin/

See https://github.com/gcushen/hugo-academic/issues/1191

static/admin/config.yml

@@ -0,0 +1,89 @@
+backend:
+  name: git-gateway
+  branch: master
+media_folder: 'static/img/'
+public_folder: 'img'
+collections:
+  - name: posts
+    label: Posts
+    label_singular: Post
+    folder: 'content/post'
+    path: '{{slug}}/index'
+    create: true  # Allow users to create new documents in this collection
+    fields:  # The fields each document in this collection have
+      - {label: "Title", name: "title", widget: "string"}
+      - {label: "Publish Date", name: "date", widget: "datetime"}
+      - {label: "Subtitle", name: "subtitle", widget: "string"}
+      - {label: "Summary", name: "summary", widget: "markdown"}
+      - label: "Draft"
+        name: "draft"
+        required: false
+        widget: "boolean"
+        default: false
+      - label: "Featured"
+        name: "featured"
+        required: false
+        widget: "boolean"
+        default: false
+      - label: "Authors"
+        name: "authors"
+        required: false
+        widget: "list"
+      - label: "Tags"
+        name: "tags"
+        required: false
+        widget: "list"
+      - label: "Categories"
+        name: "categories"
+        required: false
+        widget: "list"
+      - label: "Projects"
+        name: "projects"
+        required: false
+        widget: "list"
+      - label: "Featured Image"
+        name: "featured"
+        widget: object
+        fields:
+          - label: "Upload an image named `featured.jpg/png`"
+            name: "filename"
+            widget: "image"
+            default: "featured"
+            media_library:
+              config:
+                multiple: false
+          - {label: Caption, name: caption, widget: string, required: false}
+          - {label: "Where's the focal point in the image? Smart, Center, TopLeft, Top, TopRight, Left, Right, BottomLeft, Bottom, BottomRight.", name: focal_point, widget: string, required: false, default: "Smart"}
+          - {label: Thumbnail Only?, name: preview_only, widget: boolean, required: false, default: false}
+      - {label: "Body", name: "body", widget: "markdown"}
+  - name: "pages"
+    label: "Pages"
+    files:
+      - file: "content/privacy.md"
+        label: "Privacy Policy"
+        name: "privacy"
+        fields:
+          - {label: "Title", name: "title", widget: "string"}
+          - {label: "Publish Date", name: "date", widget: "datetime"}
+          - {label: "Subtitle", name: "subtitle", widget: "string"}
+          - {label: "Summary", name: "summary", widget: "markdown"}
+          - label: "Draft"
+            name: "draft"
+            required: false
+            widget: "boolean"
+            default: false
+          - {label: "Body", name: "body", widget: "markdown"}
+      - file: "content/terms.md"
+        label: "Terms"
+        name: "terms"
+        fields:
+          - {label: "Title", name: "title", widget: "string"}
+          - {label: "Publish Date", name: "date", widget: "datetime"}
+          - {label: "Subtitle", name: "subtitle", widget: "string"}
+          - {label: "Summary", name: "summary", widget: "markdown"}
+          - label: "Draft"
+            name: "draft"
+            required: false
+            widget: "boolean"
+            default: false
+          - {label: "Body", name: "body", widget: "markdown"}