Document Erlang support and add test

Fixes #394

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Parsing
 
+Added support for Erlang.
+
 Improved detection of binary content when the MIME type database
 incorrectly claims a text file is another format.
 

manual/src/languages_supported.md

@@ -19,6 +19,7 @@ with `difft --list-languages`.
 | Elixir          | [elixir-lang/tree-sitter-elixir](https://github.com/elixir-lang/tree-sitter-elixir)                                                                            |
 | Elm             | [elm-tooling/tree-sitter-elm](https://github.com/elm-tooling/tree-sitter-elm)                                                                                  |
 | Elvish          | [ckafi/tree-sitter-elvish](https://github.com/ckafi/tree-sitter-elvish)                                                                                        |
+| Erlang          | [WhatsApp/tree-sitter-erlang](https://github.com/WhatsApp/tree-sitter-erlang)                                                                                  |
 | Emacs Lisp      | [wilfred/tree-sitter-elisp](https://github.com/Wilfred/tree-sitter-elisp)                                                                                      |
 | Gleam           | [gleam-lang/tree-sitter-gleam](https://github.com/gleam-lang/tree-sitter-gleam)                                                                                |
 | Go              | [tree-sitter/tree-sitter-go](https://github.com/tree-sitter/tree-sitter-go)                                                                                    |

sample_files/compare.expected

@@ -43,6 +43,9 @@ sample_files/elm_before.elm sample_files/elm_after.elm
 sample_files/elvish_before.elv sample_files/elvish_after.elv
 dd6575e62ddbb4604de8e5dae7991815  -
 
+sample_files/erlang_before.erl sample_files/erlang_after.erl
+e5c989cce93d63604e4e71b83c39c5d4  -
+
 sample_files/hack_before.php sample_files/hack_after.php
 83d4a92c596b5d465ff024aa1b30be92  -