Add function-type-modifier-spacing rule

[t-kameyama]

Description

Add function-type-modifier-spacing rule
Closes #2202

Checklist

Before submitting the PR, please check following (checks which are not relevant may be ignored):

• Commit message are well written. In addition to a short title, the commit message also explain why a change is made.
• At least one commit message contains a reference Closes #<xxx> or Fixes #<xxx> (replace<xxx> with issue number)
• Tests are added
• KtLint format has been applied on source code itself and violations are fixed
• CHANGELOG.md is updated
• PR description added

Documentation is updated. See difference between snapshot and release documentation

• Snapshot documentation in case documentation is to be released together with a code change
• Release documentation in case documentation is related to a released version of ktlint and has to be published as soon as the change is merged to master
• In case of adding a new rule, it needs to be added to experimental rules documentation

[paul-dingemans]

Well done! I hand not functional remarks. But, I have refactored the code so that it better aligns with style of new code in last releases. Also added two tests to verify that unexpected newline are handled.