Adds Atom feed generation

Implements Atom feed generation for blog posts, photos, and the main site feed.

This allows users to subscribe to content using Atom-compatible feed readers.
Includes an XSLT stylesheet for rendering Atom feeds in a human-readable format in browsers.

config/_default/hugo.yaml

@@ -32,10 +32,18 @@ related:
     - name: date
       weight: 10
 
+mediaTypes:
+  application/atom+xml:
+    suffixes:
+      - xml
+
 outputFormats:
   SearchIndex:
     baseName: search
     mediaType: application/json
+  Atom:
+    mediaType: "application/atom+xml"
+    baseName: atom
 
 outputs:
   home:
@@ -43,6 +51,12 @@ outputs:
     - rss
     - SearchIndex
     - json
+    - Atom
+  section:
+    - html
+    - rss
+    - json
+    - Atom
 
 services:
   rss:

config/_default/params.yaml

@@ -6,6 +6,7 @@ images:
   - /img/Opengraph.png
 favicon: "apple-touch-icon.png"
 icon: "apple-touch-icon.png"
+icon96: "favicon-96x96.png"
 defaultColor:
   "dark" # set color mode: dark, light, auto
   # Setting it to 'auto' applies the color scheme based on the visitor's device color preference.If you don't specify anything, ignore this parameter, or leave it blank,
@@ -71,3 +72,7 @@ Hcard:
 bridgy:
   - "mastodon"
   - "bluesky"
+
+dateFormatAtomFeed: "2006-01-02T15:04:05-07:00"
+dateFormatTag: "2006"
+feedUUID: "43c22089-5c06-4cc4-8fd2-5b3563d5d257"