Update glTF-projects-data.json

[Pearces1997]

Filer has been moved to a new address, the last netlify address should have been redirecting to filer.dev already.

[javagl]

The project information has been moved to a WordPress-based backend. Updating projects should no longer be done with direct updates to the JSON file, but by clicking the "Update Project" button in the upper right of the info box of the respective project at https://ecosystem.khronos.org/

But...... the entry for Filer seems to be missing there. We're currently investigating why it is missing. (In doubt, it could just be added as a new entry, but we'll have a look at why it is missing first...)