diff --git a/Gemfile.lock b/Gemfile.lock
old mode 100755
new mode 100644
index 983d617..aa25f88
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,8 +1,8 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.7.0)
-      public_suffix (>= 2.0.2, < 5.0)
+    addressable (2.8.1)
+      public_suffix (>= 2.0.2, < 6.0)
     colorator (1.1.0)
     concurrent-ruby (1.1.6)
     em-websocket (0.5.1)
@@ -51,6 +51,8 @@ GEM
       sassc (> 2.0.1, < 3.0)
     jekyll-seo-tag (2.6.1)
       jekyll (>= 3.3, < 5.0)
+    jekyll-sitemap (1.4.0)
+      jekyll (>= 3.7, < 5.0)
     jekyll-toc (0.13.1)
       jekyll (>= 3.7)
       nokogiri (~> 1.9)
@@ -85,7 +87,7 @@ GEM
       sawyer (~> 0.8.0, >= 0.5.3)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    public_suffix (4.0.3)
+    public_suffix (5.0.0)
     rb-fsevent (0.10.3)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
@@ -120,6 +122,7 @@ DEPENDENCIES
   jekyll-relative-links
   jekyll-remote-theme
   jekyll-seo-tag
+  jekyll-sitemap
   jekyll-toc
   jekyll-twitter-plugin
   kramdown-math-katex