feat(SlashCommandBuilder): add autocomplete

[Khasms]

Please describe the changes this PR makes and why it should be merged:
Adds support for autocompletion. This is a draft because I can't figure out the types to make choices and autocomplete exclusive, so any help on this front would be appreciated. I will add tests once the types are figured out.

Relevant links:

• Announcement
• Document Application Commands Autocompletion discord/discord-api-docs#3849
• feat(Interactions): add autocomplete api types discord-api-types#205
• feat: add support for autocomplete interactions discord.js#6672

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• This PR changes the library's interface (methods or parameters added)

[codecov-commenter]

Codecov Report

Merging #42 (ea5daeb) into main (c0f7993) will decrease coverage by 1.27%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##              main      #42      +/-   ##
===========================================
- Coverage   100.00%   98.72%   -1.28%     
===========================================
  Files           18       18              
  Lines          233      236       +3     
  Branches        33       33              
===========================================
  Hits           233      233              
- Misses           0        3       +3     

Impacted Files	Coverage Δ
...s/slashCommands/mixins/CommandOptionWithChoices.ts	83.33% <0.00%> (-16.67%)	⬇️

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[suneettipirneni]

This should also include some form of validation in toJSON that checks that if autocomplete is set to true, choices are not present, and if it's set to false or undefined, then it allows choices.

[Khasms]

This should also include some form of validation in toJSON that checks that if autocomplete is set to true, choices are not present, and if it's set to false or undefined, then it allows choices.

I don't think this is needed because having proper return types that exclude the non-allowed methods is the most that has been done in the rest of the package. However, as I said in the PR description, I can't figure out how to make the types work.