Add dependabot configuration for GitHub Actions updates

[eloi010]

Add Dependabot configuration for GitHub Actions updates.

[codecov-commenter]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
743	1	742	0

View the top 1 failed test(s) by shortest run time

maru.app.MaruSupportsOsakaTest::should run network starting from Osaka()

Stack Traces | 32.7s run time

java.lang.AssertionError: 
Expecting actual:
  0
to be greater than:
  5

	at maru.app.MaruSupportsOsakaTest.should_run_network_starting_from_Osaka$lambda$2(MaruSupportsOsakaTest.kt:71)
	at org.awaitility.core.AssertionCondition.lambda$new$0(AssertionCondition.java:53)
	at org.awaitility.core.ConditionAwaiter$ConditionPoller.call(ConditionAwaiter.java:248)
	at org.awaitility.core.ConditionAwaiter$ConditionPoller.call(ConditionAwaiter.java:235)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
	at java.base/java.lang.Thread.run(Thread.java:1583)

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