JSON path support for endpoint

:clipboard: **Description**

The *dynamic* badge allows you to have a static JSON file containing multiple items, and allows you to select a part of that JSON file using the `query` parameter. You can generate multiple badges from the same JSON file, but it only lets you retrieve the message text from a particular JSON path; setting the color, label, logo, etc. must be done in the badges.io URL.

The *endpoint* badge allows you to have a static JSON file containing one item. You can set color, label, logo, and so on, but only for one item.

If the endpoint badge supported the `query` parameter, then a single file like this:

```json
[
{
"color": "brightgreen",
"label": "Outline Correctness Checks",
"message": "100%",
"schemaVersion": 1
},
{
"color": "inactive",
"label": "Shaping Checks",
"message": "SKIP",
"schemaVersion": 1
},
{
"color": "green",
"label": "Universal",
"message": "85%",
"schemaVersion": 1
},
{
"color": "green",
"label": "Fontbakery QA",
"message": "81%",
"schemaVersion": 1
}
]
```

could be used to generate four different badges dynamically.

No source files, tests, or entry points are named. Locate the endpoint badge handling and the existing dynamic badge query support, then compare how the query parameter selects JSON data. Done means an endpoint JSON collection can be queried to produce separate badges with each selected item's color, label, message, and other supported fields.

Written by the indexing model from the issue text.