Gemfile: add base64

This is needed whenever calling Octokit. So far, this has not been
necessary in the GitHub workflows, but in the next commit we will switch
to discover the ProGit downloads dynamically, which requires Octokit.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

Diff for: Gemfile

@@ -8,3 +8,5 @@ gem "rss"
 gem "asciidoctor", "~> 2.0.0"
 gem "nokogiri"
 gem "diffy"
+
+gem "base64", "~> 0.2.0"

Diff for: Gemfile.lock

@@ -4,6 +4,7 @@ GEM
     addressable (2.8.7)
       public_suffix (>= 2.0.2, < 7.0)
     asciidoctor (2.0.23)
+    base64 (0.2.0)
     diffy (3.4.3)
     faraday (2.12.2)
       faraday-net_http (>= 2.0, < 3.5)
@@ -58,6 +59,7 @@ PLATFORMS
 
 DEPENDENCIES
   asciidoctor (~> 2.0.0)
+  base64 (~> 0.2.0)
   diffy
   faraday-retry
   nokogiri
@@ -67,6 +69,7 @@ DEPENDENCIES
 CHECKSUMS
   addressable (2.8.7) sha256=462986537cf3735ab5f3c0f557f14155d778f4b43ea4f485a9deb9c8f7c58232
   asciidoctor (2.0.23) sha256=52208807f237dfa0ca29882f8b13d60b820496116ad191cf197ca56f2b7fddf3
+  base64 (0.2.0) sha256=0f25e9b21a02a0cc0cea8ef92b2041035d39350946e8789c562b2d1a3da01507
   diffy (3.4.3) sha256=4264b9e7db00d1cd426fcd32e36565779163cedc2340a95b0e6f025e71f9aaa7
   faraday (2.12.2) sha256=157339c25c7b8bcb739f5cf1207cb0cefe8fa1c65027266bcbc34c90c84b9ad6
   faraday-net_http (3.4.0) sha256=a1f1e4cd6a2cf21599c8221595e27582d9936819977bbd4089a601f24c64e54a