fix(types): improve intellisense with colors

[sean-perkins]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
  • Some docs updates need to be made in the ionic-docs repo, in a separate PR. See the contributing guide for details.
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Props that have a type of Colors, do not auto-complete with the list of available options. Instead they are replaced with a type of string.

Issue URL: N/A (internal)

What is the new behavior?

• Modified Colors type to maintain the list of custom options along with a string literal

Does this introduce a breaking change?

• Yes
• No

Other information

Example of the toast controller with this change:

Related to: #22151

Dev-build: 6.1.7-dev.11653446971.11d80e4c

[liamdebeasi]

Are type guards something we need to be concerned about here? microsoft/TypeScript#29729 (comment)

[amandaejohnston]

Works on my end 👍 I even get a nice Color | undefined type in the autocomplete, when before it was just string | undefined.

[sean-perkins]

@liamdebeasi I do not believe we take advantage of type guards in implementations with colors. I do not see any risk with this change, as the equivalent to the literal union not working in a situation that may be using type guards, would be equivalent to the existing behavior (no autocompletion/intellisense).