New String function: parseErrorHuman

[jamesdbrock]

New String function: parseErrorHuman

Returns three Strings which, when printed line-by-line, will show a nice human-readable parsing error message.

    let input = "12345six789"
    case runParser input (replicateA 9 String.Basic.digit) of
      Left err -> log $ String.joinWith "\n" $ parseErrorHuman input 20 err

Expected digit at position index:5 (line:1, column:6)
     ▼
12345six789

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Checklist:

• Added the change to the changelog's "Unreleased" section with a link to this PR and your username
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation in the README and/or documentation directory
• Added a test for the contribution (if applicable)