Add Disable Interpolation For A Heredoc String as a Ruby TIL

ruby/disable-interpolation-for-a-heredoc-string.md

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+# Disable Interpolation For A Heredoc String
+
+As a matter of convenience, a heredoc performs string interpolation by default.
+
+Here is an example of that.
+
+```ruby
+irb(main):087> word = 'taco'
+=> "taco"
+irb(main):088" puts <<-TEXT
+irb(main):089"   I want to eat a #{word}!
+irb(main):090> TEXT
+  I want to eat a taco!
+=> nil
+```
+
+A much less common scenario is that we don't want string interpolation to take
+place. For whatever reason, we want the exact string to be preserved. To
+achieve that, we can wrap the opening heredoc identifier in single quotes.
+
+As you can see, the `#{word}` portion is preserved.
+
+```ruby
+irb(main):091> word = 'taco'
+=> "taco"
+irb(main):092' puts <<-'TEXT'
+irb(main):093'   I want to eat a #{word}!
+irb(main):094> TEXT
+  I want to eat a #{word}!
+=> nil
+```
+
+This syntax puts the heredoc in single-quote mode. I left the IRB line preamble
+in for each codeblock so that you can see the difference. The first example
+(lines 88 and 89) shows the heredoc is double-quoted. The second example (lines
+92 and 93) shows the heredoc is single quoted.
+
+Note: the closing heredoc identifier (`TEXT` in this case) is not wrapped in
+single quotes, just the opening one.
+
+[source](https://ruby-doc.org/3.3.6/syntax/literals_rdoc.html#label-Here+Document+Literals)