Adds a plugin for empty hash formatting

[adamof]

Fixes #406

Adds the ability to stop the formatter from splitting empty hashes {} over multiple lines by introducing compact_empty_hash plugin.

Before formatting:

{ very_long_key_name_that_might_cause_issues: {}, another_very_long_key_name: {}, yet_another_key: {} }

After formatting without the plugin

{
  very_long_key_name_that_might_cause_issues: {
  },
  another_very_long_key_name: {
  },
  yet_another_key: {
  }
}

After formatting with the plugin

{
  very_long_key_name_that_might_cause_issues: {},
  another_very_long_key_name: {},
  yet_another_key: {}
}

[MatthiasPortzel]

Surely this change is safe to make by default, and doesn't require a plugin. I prefer opinionated software that doesn't expose unnecessary options.

[adamof]

Surely this change is safe to make by default, and doesn't require a plugin. I prefer opinionated software that doesn't expose unnecessary options.

I think that make sense, but this is one my few open-source contributions so I'm not sure how is this decided :) @kddnewton happy to hear your thoughts

[kddnewton]

Once #543 is merged, this will be the default on main. Thank you for the effort here!