manifest: support hardware/integration metadata

Device integrations would benefit from having consistent ways of linking to information about the product being integrated, integration guides (perhaps we should prefer markdown but also allow PDFs), and things like CAD file links for mounting hardware, which we could then present nicely, and allow locally downloading and storing with the extension (see bluerobotics/BlueOS-Docker#1640) as appropriate (like we're planning to do for READMEs).

I'm thinking something like

```dockerfile
LABEL hardware='{\
"integration": "https://docs.company.com/dvls/integration_guide.md",\
"components": [\
{\
"product": "My DVL 100",\
"manufacturer": "My Company",\
"details": "https://store.com/my-dvl-100",\
"image": "https://store.com/images/my-dvl-100.png",\
"purpose": "sensor for velocity measurement/positioning",\
"groups": [1]\
},\
{\
"product": "My DVL 250",\
"manufacturer": "My Company",\
"details": "https://store.com/my-dvl-250",\
"image": "https://store.com/images/my-dvl-250.png",\
"purpose": "sensor for velocity measurement/positioning",\
"groups": [2]\
},\
{\
"product": "Megamount3000",\
"manufacturer": "3D printed",\
"details": "https://printables.com/my-dvl-mount",\
"image": "https://...",\
"purpose": "attaching DVL to a vehicle",\
"groups": [1, 2]\
}\
]\
}'
```