patch 9.1.1231: filetype: SPA JSON files are not recognized

patch 9.1.1231: filetype: SPA JSON files are not recognized

Problem:  filetype: SPA (single page application) JSON files are not
          recognized (used by pipewire and wireplumber)
Solution: detect pipewire and wireplumber configuration files as spajson
          filetype, include filetype, indent and syntax scripts for this
          new filetype (David Mandelberg).

I looked at all the files found by this command to see if the syntax
highlighting looked reasonable:

```
find {~/.config,/etc,/usr/share}/{pipewire,wireplumber} -type f -name \*.conf
```

References:
*   pipewire config files: https://docs.pipewire.org/page_config.html
*   wireplumber config files:
    https://pipewire.pages.freedesktop.org/wireplumber/daemon/configuration/conf_file.html
    and
*   https://pipewire.pages.freedesktop.org/wireplumber/daemon/locations.html

closes: #16950

Signed-off-by: David Mandelberg <david@mandelberg.org>
Signed-off-by: Christian Brabandt <cb@256bit.org>