Justfile: add command to show extension's configuration on container

Author: thePanz

Diff for: Justfile

@@ -45,6 +45,10 @@ run-cs-fix *options:
 tests-legacy:
     {{ dockerExec }} php data/bin/symfony symfony:test --trace
 
+# Show the given PHP extensions's configuration from the running PHP container
+php-ext-config extname:
+    {{ dockerExec }} php --ri {{ extname }}
+
 # Setup and initialize the project (docker image must be running)
 setup:
     git submodule update --checkout --recursive --force