Allow .ts extension for compiled messages file

Is your feature request related to a problem? Please describe. I am always frustrated when I have to allow ts to import js messages (eslint) or when I have to reconfigure the ts config to serve .mjs files.

Having imported import { messages } from './locales/en/messages.mjs'; I need to:

• in *.mjs case allow typescript to serve multiple extensions
• in *.js case disable import extensions check

Describe proposed solution I would like to configure the extension like this:

.linguirc
{
 ...
 "compileNamespace": "es",
 "compileExtension": "ts",
}

Describe alternatives you’ve considered There is always alternative to setup eslint but it does not sound like a big deal to have it in config. I have also tried to rename the file to *.ts extension and it works like charm, (thank you @laszbalo). Example below.

    "lingui:compile": "lingui compile && for f in $(find ./src/locales/* -type f -name '*.mjs'); do mv \"$f\" \"${f%.mjs}.ts\"; done"

Additional context I am using standard Create-React-App bundler with default settings, with airbnb and recommended eslint plugins.

[semoal]

Released in 3.4.0 🥳, also with the new version we accept lingui.config.ts thanks to @FredyC

[mjpieters]

Note that lingui compile --typescript merely adds a .d.ts file with a type definition for the .js file. It is also undocumented (but so is a lot of lingui 3, it appears).