Use linting rules that require type checking

[netux]

This is a continuation of the addition of eslint to lint Typescript files.

The default @typescript-eslint/recommended doesn't include rules that require type checking, so this PR includes @typescript-eslint/recommended-requiring-type-checking rules to check for those too.

Due to the new rules being enforced, some miscellaneous changes were done:

• Modified no-void rule on eslint to allow for "void" at the beginning of statements. This is useful for calling promises that we don't care about the result of.
• Remove pad function from util. Functions that used it now use String.padStart() or String.padEnd().
• Use fs/promise instead of fs wherever possible to avoid blocking operations.
• Make util.find resolve to false when no valid type is given.
• Move util.getPrefix to the config command file..
• await or void all promises.
• Make Command.execute return Promise | void.
• Allow presence to be unset/null in config.

This PR also:

• Adds a tsconfig.json file.
• Adds scripts for verifying that Typescript files don't have errors.
• Makes !ping return per shard ping instead of the last pings. This is because Discord.js v12 stopped providing this information to us.
• Fixes !config create not checking database errors correctly.