Gleam support (#71)

* Gleam support

Related to exercism/gleam#32 (comment)

* Oops, whitespace

lib/languages/gleam.txt

@@ -0,0 +1,5 @@
+!e
+//\p
+///\p
+////\p
+import

test/languages/gleam_test.rb

@@ -0,0 +1,74 @@
+require "test_helper"
+
+module SnippetExtractor
+  module Languages
+    class GleamTest < Minitest::Test
+      def test_full_example
+        code = <<~CODE
+          //// This is a file
+          //// With some comments in it
+
+          // And a blank line ⬆️
+          // It has some imports like this:
+          import gleam/erlang
+          import gleam/erlang/process.{Subject}
+
+          /// And then eventually the code
+          pub fn two_fer(name: String) -> String {
+            todo
+          }
+        CODE
+
+        expected = <<~CODE
+          pub fn two_fer(name: String) -> String {
+            todo
+          }
+        CODE
+
+        assert_equal expected, ExtractSnippet.(code, :gleam)
+      end
+
+      def test_extended_example
+        code = <<~CODE
+          //// This is a file
+          //// With some comments in it
+
+          // And a blank line ⬆️
+          // It has some imports like this:
+          import gleam/erlang
+          import gleam/erlang/process.{Subject}
+
+          /// And then eventually the code
+          pub fn two_fer(name: String) -> String {
+            todo// with comments
+          }
+
+          // Here is a comment
+          /// And a documentation comment
+          pub type TwoFer {
+            TwoFer(name: String)
+          }
+
+          const a = 1
+          const b = 1
+          const c = 1 // More, but this is over 10 lines so it wont appear
+        CODE
+
+        expected = <<~CODE
+          pub fn two_fer(name: String) -> String {
+            todo
+          }
+
+          pub type TwoFer {
+            TwoFer(name: String)
+          }
+
+          const a = 1
+          const b = 1
+        CODE
+
+        assert_equal expected, ExtractSnippet.(code, :gleam)
+      end
+    end
+  end
+end