Set up a file watcher that automatically rebuilds all the tag manager container when a file changes

[tsteur]

Only for development. If you otherwise change anything in TagManager or any of the Tags/Triggers/Variables you otherwise always need to manually execute the tagmanager:regenerate-released-containers command to test the changes.

Something similar to https://github.com/matomo-org/matomo/blob/4.x-dev/tests/angularjs/Gruntfile.js#L14-L32 where we then call ./console tagmanager:regenerate-released-containers every time a container changes.

Ideally if tagmanager.js changes we maybe (or maybe not) need to call cat javascripts/tagmanager.js | java -jar ../../js/yuicompressor-2.4.8.jar --type js --line-break 1000 | sed 's/^[/][*]/\/*!/' > javascripts/tagmanager.min.js (although in https://github.com/matomo-org/tag-manager/issues/351 we also add an action for this so probably not needed)

No preference on what tool we use for this.