workbox database support

Is it possible to integrate into an existing `workbox` database?

When using service workers - `workbox` (PWA solution for front-end) creates a database where failed HTTP requests are stored. It looks like this:




also, see that key path 'id' is used.

So, I am trying to connect to this database and retrieve all keys and values:

```
import localforage from "localforage";

var store = localforage.createInstance({
name: "workbox-background-sync",
storeName: "requests",
});
```

and

```
store
.keys()
.then(async (keys) => {
for (let key in keys) {
console.log(key); // 0 - index
var itemKey = keys[key]; // 76
var val = await store.getItem(String(itemKey));
console.log(val ); // null !!!
}
})
.catch(function (err) {
console.log(err);
});
```

The `localforage` is able to get the keys just fine and loop over them. But the value is retrieved as `null`. No errors are thrown.

Furthermore, out of curiosity I tried inserting my own data into the store (not because I actually plan on using this):

```
const add = async () => {
try {
var res = await store.setItem(56, { id: 56, data: "fasdf" });
} catch (error) {
console.error(error);
}
};
```

and the exception is thrown:

> DOMException: Failed to execute 'put' on 'IDBObjectStore': The object store uses in-line keys and the key parameter was provided.

So my question is - is the `workbox` database not compatible with `localForage`? What exactly makes it incompatible and what solutions (maybe other `indexeddb` wrappers) would allow me to read the data from it?

My aim at this point is just reading the data so it would be ideal if `localforage` could do at least just that..

Start by reading the localForage database-driver implementation and its IndexedDB handling, then compare it with the Workbox database described in the issue: the workbox-background-sync database and requests store, including the inline id key path. Reproduce the keys() and getItem() behavior and determine what compatibility or documentation change would be needed for reading those records.

Written by the indexing model from the issue text.