Support ignoring missing translations for additional locales in compile --strict

Problem Description

We use a generated locale like longest-LOCALE for UI stress-testing.

lingui compile --strict already ignores missing translations for pseudoLocale, but it still fails for other generated locales like longest-LOCALE.

Example:

export default defineConfig({
  locales: ["en-US", "longest-LOCALE", "pseudo-LOCALE"],
  sourceLocale: "en-US",
  pseudoLocale: "pseudo-LOCALE",
})

Proposed Solution

Would it make sense to support something like:

export default defineConfig({
  locales: ["en-US", "longest-LOCALE", "pseudo-LOCALE"],
  sourceLocale: "en-US",
  pseudoLocale: "pseudo-LOCALE",
  ignoreMissing: ["longest-LOCALE"],
})

This would let compile --strict stay strict for real locales, while skipping missing-translation errors for generated ones.

Additional Context

My main question is whether longest-LOCALE should be treated as:

• another generated locale similar to pseudoLocale
• or just a locale excluded from strict missing checks via something like ignoreMissing

Start with the compile --strict handling and the existing pseudoLocale behavior described in the issue. Determine whether additional generated locales should use a new ignoreMissing configuration or share the pseudo-locale treatment. Done means strict compilation still reports missing translations for real locales while skipping the configured generated locale.