Add Encode A String As URL-Safe Base64 as a ruby til

ruby/encode-a-string-as-url-safe-base64.md

@@ -0,0 +1,19 @@
+# Encode A String As URL-safe Base64
+
+Ruby's standard lib comes with a [Base64
+module](https://ruby-doc.org/stdlib-2.1.4/libdoc/base64/rdoc/Base64.html)
+with a number of utilities for encoding and decoding data as
+[Base64](https://en.wikipedia.org/wiki/Base64). One of the methods it
+provides is `urlsafe_encode64`.
+
+```ruby
+> require 'base64'
+true
+> Base64.urlsafe_encode64('hello')
+"aGVsbG8="
+> Base64.urlsafe_encode64('1')
+"MQ=="
+```
+
+You can pass it any string and it will create a URL-safe Base64 encoded
+representation of that string.