Enhancement: Ability to define a "media file metadata changed" event handler where we could execute a script when media file metadata is changed.

[polynook]

Is your feature request related to a problem? Please describe.
When working with media files, sometimes their metadata needs to be changed. If I change any metadata (e.g., image's filename, caption, or alt text), the changes aren't propagated to the places in the content where this metadata is used.

Describe the solution you'd like
Ability to define a "metadata changed" event handler where we could execute some script when metadata is changed.
This enhancement would also go well together with the enhancement discussed here #666.

Describe alternatives you've considered
We can note down the old metadata value, change it to a new value, then use VS Code built-in search functionality to replace all occurrences of the old value with the new value. However, this is cumbersome and might be error prone. With this proposed enhancement, we would have all the power of Node.js to parse and update the content to reflect the new metadata values based on our specific rules.

[estruyf]

Thanks @polynook for the suggestion!