[jekyll] update jekyll

Gemfile.lock

@@ -15,10 +15,10 @@ GEM
     colorator (1.1.0)
     commonmarker (0.17.13)
       ruby-enum (~> 0.5)
-    concurrent-ruby (1.1.3)
+    concurrent-ruby (1.1.7)
     dnsruby (1.61.2)
       addressable (~> 2.5)
-    em-websocket (0.5.1)
+    em-websocket (0.5.2)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0.6.0)
     ethon (0.11.0)
@@ -27,7 +27,7 @@ GEM
     execjs (2.7.0)
     faraday (0.15.3)
       multipart-post (>= 1.2, < 3)
-    ffi (1.9.25)
+    ffi (1.13.1)
     forwardable-extended (2.6.0)
     gemoji (3.0.0)
     github-pages (192)
@@ -185,7 +185,7 @@ GEM
       jekyll-seo-tag (~> 2.0)
     jekyll-titles-from-headings (0.5.1)
       jekyll (~> 3.3)
-    jekyll-watch (2.1.2)
+    jekyll-watch (2.2.1)
       listen (~> 3.0)
     jemoji (0.10.1)
       gemoji (~> 3.0)
@@ -212,16 +212,16 @@ GEM
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     public_suffix (2.0.5)
-    rb-fsevent (0.10.3)
-    rb-inotify (0.9.10)
-      ffi (>= 0.5.0, < 2)
+    rb-fsevent (0.10.4)
+    rb-inotify (0.10.1)
+      ffi (~> 1.0)
     rouge (2.2.1)
     ruby-enum (0.7.2)
       i18n
     ruby_dep (1.5.0)
     rubyzip (1.2.2)
-    safe_yaml (1.0.4)
-    sass (3.7.2)
+    safe_yaml (1.0.5)
+    sass (3.7.4)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
@@ -249,4 +249,4 @@ DEPENDENCIES
   tzinfo-data
 
 BUNDLED WITH
-   1.17.1
+   1.17.2

README.md

@@ -1,5 +1,15 @@
 # rf-lab.github.io
 
+## Update
+[Official manual](https://jekyllrb.com/docs/upgrading/)
+```
+bundle update
+```
+or if no bundle
+```
+gem update jekyll
+```
+
 ## Development
 ```
 # rm -rf _site ; bundle exec jekyll serve