feat: allow for aliasing icons

[RebeccaStevens]

Description

Allows for aliases to be defined as:

{
  "chevron-left": "ri:arrow-left-s-line",
  "chevron-up": "ri:arrow-up-s-line",
  "chevron-right": "ri:arrow-right-s-line",
  "chevron-down": "ri:arrow-down-s-line",
  // ...
}

Aliases can either be defined in the settings.json or (inclusive) in linked JSON files.

Additionally, users can opt-in to ignoring unaliased icons.

Linked Issues

fix #58

Additional context

Adds options:

• customAliases
• customAliasesJsonPaths
• customAliasesOnly

[RebeccaStevens]

@antfu Sorry for the ping, I know you must be busy; just didn't want this to be forgotten about.

[antfu]

I am not sure if it's necessary to introduce so many options. Also, I think manually listing all icons one to one might be a scalable solution. I think we should better have a more generalized design.

[RebeccaStevens]

I am not sure if it's necessary to introduce so many options.

• customAliases probably isn't needed as I'd imagine everyone would rather use customAliasesJsonPaths, so I'll remove it.
• customAliasesOnly could probably also be removed, but I thought I'd add it for those that want to use it as an extra step of visual validation that they are using allowed icons (in the case where all allowed icons are aliased). ~Would you like me to remove this one too?~ - Personally, I would like to use this feature too, mostly for the auto-complete limiting.

listing all icons one to one might be a scalable solution

I assume you meant "might not be a scalable solution".

Listing all icons one to one is what my use case calls for so I would like to have this option. Also there's already the customCollectionIdsMap for aliasing full collections.