fix: Type exported configs correctly

[porada]

This PR tightens the types on the exported configs.

Given the plugin referenced itself, so this isn’t the most elegant type definition, but it does the job and improves the overall consumer experience. satisfies wouldn’t be enough in this case.

Fixes #67.
Closes #68.

Before

export default defineConfig({
    rules: {
        ...(pluginPerformance.configs!.modernization as Linter.Config) .rules,
        ...(pluginPerformance.configs!.moduleReplacements as Linter.Config).rules,
        ...(pluginPerformance.configs!.performanceImprovements as Linter.Config).rules,
    },
});

After

export default defineConfig({
    rules: {
        ...pluginPerformance.configs.modernization.rules,
        ...pluginPerformance.configs.moduleReplacements.rules,
        ...pluginPerformance.configs.performanceImprovements.rules,
    },
});

[porada]

This could be tightened ever further with as const satisfies NonNullable<ESLint.Plugin['configs']>, but I thought the following plugin.configs = configs would be enough.