Adding a param to customize the access modifier

[txaiwieser]

This is very useful to being able to use SwiftGen from inside a framework. And use the generated code in the main target.

[AliSoftware]

Nice idea, this looks promising!

How about storing the {% if param.accessModifier %}{{ param.accessModifier}} {% endif %} block that you have to repeat in a lot of places… into a local Stencil variable using {% set access %}…{% endset %}?
This would allow you to use {{access}} directly all the time in all situations (if it's not set it's gonna be replaced with nothing (the empty string) and if it's set it's gonna be replaced by the access modifier and its space afterwards)

Also, don't forget to:

• Apply the same logic to all templates, not just fonts/swift4
• Update the unit tests too
• credit yourself in the CHANGELOG!

[AliSoftware]

@txaiwieser Ping 😉
Would love to see this go forward. You just need to:

• Replicate the same changes to all the templates (and not just fonts/swift4)
• Add some unit tests for this param (just duplicate another unit test already testing another parameter and change the tested parameter for accessModifier ; you can then use the "Generate fixtures" scheme to generate the expected outputs and have all your tests ready for you)
• and last but definitely not least: add a CHANGELOG entry to credit yourself!

[AliSoftware]

I've open #84 to supersede this PR with a slight different approach, as it seems this PR went a little stale.