chore: update the doc and improve phpstan annotations

docs/Gemfile.lock

@@ -3,6 +3,7 @@ GEM
   specs:
     addressable (2.8.6)
       public_suffix (>= 2.0.2, < 6.0)
+    base64 (0.2.0)
     bigdecimal (3.1.7)
     colorator (1.1.0)
     concurrent-ruby (1.2.3)
@@ -57,18 +58,18 @@ GEM
     mercenary (0.4.0)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    public_suffix (5.0.4)
-    rake (13.1.0)
+    public_suffix (5.0.5)
+    rake (13.2.1)
     rb-fsevent (0.11.2)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
     rexml (3.2.6)
     rouge (4.2.1)
     safe_yaml (1.0.5)
-    sass-embedded (1.72.0)
+    sass-embedded (1.76.0)
       google-protobuf (>= 3.25, < 5.0)
       rake (>= 13.0.0)
-    sass-embedded (1.72.0-x86_64-linux-gnu)
+    sass-embedded (1.76.0-x86_64-linux-gnu)
       google-protobuf (>= 3.25, < 5.0)
     terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
@@ -80,13 +81,15 @@ PLATFORMS
   x86_64-linux
 
 DEPENDENCIES
+  base64
   bigdecimal
   csv
   jekyll
   jekyll-redirect-from
   jekyll-seo-tag
   jekyll-sitemap
-  webrick (~> 1.8)
+  kramdown-parser-gfm
+  webrick
 
 BUNDLED WITH
    2.5.6