* Handle SIGTERM
Resolve#781
* Add `Caught signal ...` messages
Container log when sending a `SIGHUP` signal and then a `SIGTERM` signal using
`docker kill --signal ...` :
```
Starting tileserver-gl v4.4.8
[INFO] Automatically creating config file for zurich_switzerland.mbtiles
[INFO] Only a basic preview style will be used.
[INFO] See documentation to learn how to create config.json file.
Run with --verbose to see the config file here.
Starting server
Listening at http://[::]:8080/
Startup complete
Caught signal SIGHUP, refreshing
Stopping server and reloading config
Starting server
Listening at http://[::]:8080/
Startup complete
Caught signal SIGTERM, stopping gracefully
```
Note that the numeric signal values, as used in the shell version, were
replaced by signal names, as used in nodeJS.
* run 'npm run lint:js:fix'
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Co-authored-by: acalcutt <acalcutt@techidiots.net>
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