Include the version in the App Manifest and require the developer to update it

**Is your feature request related to a problem? Please describe (REQUIRED):**
From Defold version to Defold version, the variations of libraries and symbols in `.appmanifest` changes sometimes. I personally keep forgetting to update this file all the time. And if a build of a game on the new version of the engine fails to link because of missing symbols in the log, you don't immediately realise that it's because of the old `.appmanifest`.

**Describe the solution you'd like (REQUIRED):**
So it would be cool to add a ‘version’ to this file and when the version of the file differs from the version in the engine, require the developer to open the file and just double-check the set checkboxes.

**Additional context (OPTIONAL):**
To be honest, updating the app manifest is rarely needed, as the Defold team does a great job 🤗 and rarely breaks backwards compatibility! But I've been looking at how many extra flags adds the enabling of WebGPU, which made me think that versioning this file would come in really handy.

P.S. It would just save the headache of users opening up their 5 year old projects from the Defold 1.2.xxx era and screaming "why doesn't it work, aaaaaa!!".