Rule Request: Float-type literal decimal

New Issue Checklist

• Updated SwiftLint to the latest version
• I searched for existing GitHub issues

New rule request

1. Why should this rule be added? Share links to existing discussion about what the community thinks about this.

I've been reading a lot of open source Swift code lately and I see both let someFloat = 1 and let someFloat = 1.0 being used. Would be nice to enforce consistency here, either way.

2. Provide several examples of what would and wouldn't trigger violations.

If you have set it to enforce .0:

Would trigger:

let foo: Double = 3

let bar: CGFloat = 0

Would not trigger:

let foo = 3.0

let bar: CGFloat = 0.0

3. Should the rule be configurable, if so what parameters should be configurable?

Yes, it should be configurable whether to enforce or disallow the .0 part in float-type literals.

4. Should the rule be opt-in or enabled by default? Why?
   See README.md for guidelines on when to mark a rule as opt-in.

Opt-in

Review the requested examples and configuration requirement, then read README.md's opt-in rules guidance before examining how existing SwiftLint rules are structured. The work is complete when the proposed opt-in rule consistently handles the shown float-type literals and supports choosing whether .0 is enforced or disallowed.