Rich Text with Placeholders in t.rich Not Rendering Correctly - Displays Key Instead of Content

Description

When using t.rich with translations that contain placeholders like <strong1>, the expected behavior is that the content between these placeholders is rendered according to the mapping provided in the t.rich call. However, due to the bug, the output is only the translation key (e.g., IndexPage.subtitle) rather than the processed translation content.

Verifications

[X] I've verified that the problem I'm experiencing isn't covered in the docs.
[X] I've searched for similar, existing issues on GitHub and Stack Overflow.
[X] I've compared my app to a working example to look for differences.

Mandatory reproduction URL

https://github.com/RedEagle-dh/next-intl-bug-placeholders-not-rendered

Reproduction description

Clone the repository:

git clone https://github.com/redeagle-dh/next-intl-bug-placeholders-not-rendered.git
cd next-intl-bug-placeholders-not-rendered

Install dependencies: Make sure you have Node.js installed, then run:
```
yarn
```
Start the development server:
```
yarn dev
```
Open the application in your browser: Navigate to http://localhost:3000.
Trigger the bug:
- You should already see the output on the main page.
- The translation key IndexPage.subtitle will be displayed instead of the expected text content with the rich text formatting applied.

Expected behaviour

The t.rich function should correctly parse the placeholders in the translation (e.g., <strong1>...</strong1>) and render the content according to the provided mappings. For example, if the translation in de.json is:

{
  "IndexPage": {
    "title": "Hello!",
    "subtitle": "<strong1>Welcome</strong1> to Next.js!"
  }
}

The expected output should display Welcome and to Next.js! wrapped in the appropriate React components as defined in the t.rich call.

amannn / next-intl