Implement issue #2: Support multiple repositories

[nicokosi]

Implement issue #23

• Parse repository separated by commas
• Make parallel GitHub requests
• Check that the executable built with GraalVM still works

[nicokosi]

Kotlin coroutines are visibly still not compatible with GraalVM 19.2.0.1 😭:

Using java version 19.2.0.1-grl in this shell.
Copying 'libsunec' shared library (Sun Elliptic Curve crypto):
'libsunec' shared library has been copied! ✅
Build executable from JAR via GraalVM:
Downloading: Component catalog from www.graalvm.org
Processing component archive: Native Image
Downloading: Component native-image: Native Image  from github.com
Installing new component: Native Image (org.graalvm.native-image, version 19.2.0.1)
[pullpitoK:23139]    classlist:   2,250.81 ms
[pullpitoK:23139]        (cap):   5,271.10 ms
[pullpitoK:23139]        setup:   6,765.94 ms
[pullpitoK:23139]     analysis:   3,291.25 ms
Error: Non-reducible loop
Detailed message:
Call path from entry point to pullpitok.AppKt$displayEvents$2.invokeSuspend(Object):
	at pullpitok.AppKt$displayEvents$2.invokeSuspend(App.kt)
	at pullpitok.AppKt$displayEvents$2.invoke(App.kt)
	at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:91)
	at kotlinx.coroutines.CoroutineScopeKt.coroutineScope(CoroutineScope.kt:180)
	at pullpitok.AppKt.displayEvents(App.kt:43)
	at pullpitok.AppKt$main$2.invokeSuspend(App.kt:16)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlin.coroutines.ContinuationKt.startCoroutine(Continuation.kt:114)
	at kotlin.coroutines.jvm.internal.RunSuspendKt.runSuspend(RunSuspend.kt:19)
	at pullpitok.AppKt.main(App.kt)
	at com.oracle.svm.core.JavaMainWrapper.runCore(JavaMainWrapper.java:151)
	at com.oracle.svm.core.JavaMainWrapper.run(JavaMainWrapper.java:186)
	at com.oracle.svm.core.code.IsolateEnterStub.JavaMainWrapper_run_5087f5482cc9a6abc971913ece43acb471d2631b(generated:0)

Cf. oracle/graal#366.