feat: add new input to allow include statements at the top of formula class

[unfrgivn]

Following the official guidance here for building formulas that deploy python apps. Homebrew provides built-in helper methods for different languages so I have called this generically formula_includes to differentiate that they are inside the Formula (open to suggestions on naming). In order to use these, they must be included inside the Formula class, but outside any of the blocks that Justintime50/homebrew-releaser currently allows for.

I have added a generic placeholder that sits in the global scope of the Formula class, immediately following the metadata properties.

Example formula.rb

class TestGenerateFormula < Formula
  desc "Tool to release scripts, binaries, and executables to github"
  homepage "https://github.com/Justintime50/test-generate-formula"
  ...

  include Language::Python::Virtualenv <-- HERE IS THE NEW TEMPLATE BLOCK

  depends_on "bash" => :build
  depends_on "gcc"

  def install
    ...

[unfrgivn]

Let me get your thoughts @Justintime50 before I do any further clean up on this.

[Justintime50]

Awesome! I'm for it. This will enable Python apps installable correct?

A few thoughts:

1. Based on the docs provided, it looks like homebrew wants that includes line as the first item in the formula even before the metadata properties followed by a newline, let's follow suit in case there is a brew audit rule about it so we stay compliant.
2. Out of curiosity, what other includes are possible?
3. The lint is failing because I bumped the dev deps inbetween your last PR. You'll want to just clean install and then just lint-fix to pull in the new flake8/mypy rules and fix them. It looks like it corrected them back to the old rules based on your locally installed deps which no longer match the main branch.
4. We'd want a new formula test to ensure that when the param is passed, the output formula looks like we'd expect. You'll notice there are a bunch of output formula in the test dir. Follow the examples of previous tests to add a new one and assert the new includes line is present and inspect the output file (ensure it gets committed)

[unfrgivn]

Looks like Brew has Ruby packages for a few languages with some helper functions, https://rubydoc.brew.sh/Language.html.

Not my area of expertise, but I would assume you could include any valid Ruby package and then reference it inside in the formula.

[unfrgivn]

Brew audit actually failed with extra whitespace. Fixing that last issue now.

[Justintime50]

Looks great! Small suggestion,

TLDR: the test could be even simpler to ensure we are only testing what we care about in this particular case since we have tests for those other items elsewhere.

[Justintime50]

v0.19.0 (or v1) shipped with the feature, thanks for adding that! 😃