ts-transformer: Description is not available to formatter unless it is a string

[psalv]

Which package?

ts-transformer

Describe the bug

If the description field of MessageDescriptor is an object (rather than a string) it will not be available when reading messages in a custom formatter.

Example

<FormattedMessage 
    defaultMessage="Foo" 
    description={{text: "Foo description", contextImage="https://foo.com"}}
/>

To Reproduce

Reproducible Steps/Repo

Steps to reproduce the behavior:

1. Change the value of description on a FormattedMessage from "Foo" to {text: "Foo"}
2. Run a custom formatter which prints out the messages
3. The description will be missing for the given element

Expected behavior

Descriptions should support both string and object-type values (which would align with its Typescript prototype string | object) to allow for custom context to be provided such as images and group IDs.

Additional context

As discussed in #3363

This is where I believe the change needs to be made to support extracting objects:

formatjs/packages/ts-transformer/src/transform.ts

Line 245 in dfcf87e

if (name && ts.isIdentifier(name) && initializer) {