Merge after #548
Adds a new [.pmtiles](https://protomaps.com/docs/pmtiles/) backend.
Supports all formats like png, vector, etc.
From CLI, can be as easy as adding a path to a directory that contains a
.pmtiles file:
```bash
# All *.pmtiles files in this dir will be published.
# The filename will be used as the source ID
martin ./tests/fixtures
```
From configuration file, the path can be specified in a number of ways:
```yaml
pmtiles:
paths:
# scan this whole dir, matching all *.pmtiles files
- /dir-path
# specific pmtiles file will be published as pmtiles2 source
- /path/to/pmtiles2.pmtiles
sources:
# named source matching source name to a single file
pm-src1: /tmp/pmtiles.pmtiles
# named source, where the filename is explicitly set. This way we will be able to add more options later
pm-src2:
path: /tmp/pmtiles.pmtiles
```
Fixes#508
