Upgrade to Ruby 3.0

Ruby 3 should be faster than Ruby 2, which should mean a little less
time waiting for jekyll to build the site.

[Ruby 3.0.0 Released](https://www.ruby-lang.org/en/news/2020/12/25/ruby-3-0-0-released/)

Aside from the speed increase, it isn't a bad idea to keep up-to-date
with the latest version of Ruby.

Jekyll is compatible with Ruby 3 with the caveat that you need to add
WEBrick as a dependency when upgrading: jekyll/jekyll#8523

I've run `jekyll serve` locally and the site builds without errors and
looks good in a browser. Especially considering this is a static site,
that's good enough for me!

Author: mkasberg

.ruby-version

@@ -1 +1 @@
-2.7.1
+3.0.2

Gemfile

@@ -4,6 +4,10 @@ gem 'jekyll', '~> 4.1'
 gem 'jekyll-redirect-from', '~> 0.16'
 gem 'jekyll-paginate', '~> 1.1'
 
+# Need Webrick as an explicit dependency after upgrading to Ruby 3+
+# https://github.com/jekyll/jekyll/issues/8523
+gem "webrick", "~> 1.7"
+
 group :jekyll_plugins do
     gem 'jekyll_html_truncatewords', '~> 0.1.2'
 end

Gemfile.lock

@@ -67,6 +67,7 @@ GEM
     terminal-table (2.0.0)
       unicode-display_width (~> 1.1, >= 1.1.1)
     unicode-display_width (1.8.0)
+    webrick (1.7.0)
 
 PLATFORMS
   ruby
@@ -76,6 +77,7 @@ DEPENDENCIES
   jekyll-paginate (~> 1.1)
   jekyll-redirect-from (~> 0.16)
   jekyll_html_truncatewords (~> 0.1.2)
+  webrick (~> 1.7)
 
 BUNDLED WITH
-   2.1.4
+   2.2.22