Add 'type-literal-delimiter' rule

[andy-hanson]

PR checklist

• Addresses an existing issue: #0000
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

Added the type-literal-delimiter rule, which prefers { x: number, y: string } over { x: number; y: string }.

CHANGELOG.md entry:

[new-rule] type-literal-delimiter

[nchen63]

does it handle space before/after delimiter?

[andy-hanson]

Not currently, no. I think that would be more appropriate for the whitespace rule.

[nchen63]

I'm asking if it would erroneously flag { a: b , c: d } or { a: b, c: d }. Should probably have a unit test

[andy-hanson]

Oh, gotcha. Added a test.

[adidahiya]

wait, this feels pretty inconsistent with how we write out interfaces... users are going to be pretty confused when tslint recommends this format:

type Foo {
  a: number,
  b: number,
}

interface Bar {
  a: number;
  b: number;
}

can we please make the default config prefer semicolons?

[andy-hanson]

@adidahiya If so, then the current trailing-comma wouldn't handle checking for the last token. Maybe trailing-comma should be updated to check for type literal delimiters too, regardless of the kind used?

[adidahiya]

@andy-hanson no, I think we can leave trailing-comma as-is. I think this rule (type-literal-delimiter) should enforce the trailing semicolon.