Update dependencies

Everything is now on its latest available version, except for liquid,
terminal-table, and unicode-display_width, for which Jekyll specifies
lower major versions.

This also updates the .gitignore, since Jekyll now generates a
.jekyll-cache directory.

The README doesn't specify a testing procedure, but I've run `jekyll
serve` locally and clicked on all the navigation menu links and it
looks fine.

Author: thatandromeda

.gitignore

@@ -1,3 +1,4 @@
 _site
 .sass-cache
 .jekyll-metadata
+.jekyll-cache

Gemfile

@@ -8,13 +8,11 @@ source "https://rubygems.org"
 #
 # This will help ensure the proper Jekyll version is running.
 # Happy Jekylling!
-gem "jekyll", "~> 3.9.1"
+gem "jekyll", "~> 4.2.0"
 
 # This is the default theme for new Jekyll sites. You may change this to anything you like.
 gem "minima", "~> 2.0"
 
-gem "kramdown-parser-gfm"
-
 # If you want to use GitHub Pages, remove the "gem "jekyll"" above and
 # uncomment the line below. To upgrade, run `bundle update github-pages`.
 # gem "github-pages", group: :jekyll_plugins

Gemfile.lock

@@ -12,27 +12,29 @@ GEM
     ffi (1.15.4)
     forwardable-extended (2.6.0)
     http_parser.rb (0.8.0)
-    i18n (0.9.5)
+    i18n (1.8.11)
       concurrent-ruby (~> 1.0)
-    jekyll (3.9.1)
+    jekyll (4.2.1)
       addressable (~> 2.4)
       colorator (~> 1.0)
       em-websocket (~> 0.5)
-      i18n (~> 0.7)
-      jekyll-sass-converter (~> 1.0)
+      i18n (~> 1.0)
+      jekyll-sass-converter (~> 2.0)
       jekyll-watch (~> 2.0)
-      kramdown (>= 1.17, < 3)
+      kramdown (~> 2.3)
+      kramdown-parser-gfm (~> 1.0)
       liquid (~> 4.0)
-      mercenary (~> 0.3.3)
+      mercenary (~> 0.4.0)
       pathutil (~> 0.9)
-      rouge (>= 1.7, < 4)
+      rouge (~> 3.0)
       safe_yaml (~> 1.0)
-    jekyll-feed (0.10.0)
-      jekyll (~> 3.3)
-    jekyll-sass-converter (1.5.2)
-      sass (~> 3.4)
-    jekyll-seo-tag (2.5.0)
-      jekyll (~> 3.3)
+      terminal-table (~> 2.0)
+    jekyll-feed (0.15.1)
+      jekyll (>= 3.7, < 5.0)
+    jekyll-sass-converter (2.1.0)
+      sassc (> 2.0.1, < 3.0)
+    jekyll-seo-tag (2.7.1)
+      jekyll (>= 3.8, < 5.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
     kramdown (2.3.1)
@@ -43,9 +45,9 @@ GEM
     listen (3.7.0)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
-    mercenary (0.3.6)
-    minima (2.5.0)
-      jekyll (~> 3.5)
+    mercenary (0.4.0)
+    minima (2.5.1)
+      jekyll (>= 3.5, < 5.0)
       jekyll-feed (~> 0.9)
       jekyll-seo-tag (~> 2.1)
     pathutil (0.16.2)
@@ -57,19 +59,18 @@ GEM
     rexml (3.2.5)
     rouge (3.26.1)
     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)
-      rb-inotify (~> 0.9, >= 0.9.7)
+    sassc (2.4.0)
+      ffi (~> 1.9)
+    terminal-table (2.0.0)
+      unicode-display_width (~> 1.1, >= 1.1.1)
+    unicode-display_width (1.8.0)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
-  jekyll (~> 3.9.1)
+  jekyll (~> 4.2.0)
   jekyll-feed (~> 0.6)
-  kramdown-parser-gfm
   minima (~> 2.0)
   tzinfo-data