Enforce UTF-8 encoding when reading source files (fixes build on Windows)

[NPException]

[EDIT-2] Here's the error I get: (there's a total of 6 of these errors, all complaining about an unmappable character for the windows-1552 encoding)

ReportEntryExtensionTests.java:377: error: unmappable character (0x9D) for encoding windows-1252
	"And the only word there spoken was the whispered word, “Lenore?�?",

Due to Gradle using the operating system default encoding, the build failed on Windows. Explicitly telling Gradle to use UTF-8 solves that issue.

[EDIT] I don't know why the automatic Windows build was passing without this. Didn't work on my machine. 😅

I have no idea if this is the preferred way of setting the encoding, but it was the first working thing I could find.

I also found this snippet as a general solution, but it's from a post from 2012, and I have no clue how to translate it to the Gradle Kotlin:

tasks.withType(Compile) {
    options.encoding = 'UTF-8'
}

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[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

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[NPException]

Quick note: I did a bit of research, and the reason the automated Windows builds passed, is that Windows Server 2019 uses UTF-8 as the system default encoding.
Unfortunately, good old Windows 10 uses Windows-1252 encoding.

[Bukama]

Do you replay to #249, which was based on my Discord message from May 1st?

ReportEntryExtensionTests.java:377: error: unmappable character for encoding Cp1252
                                                                "And the only word there spoken was the whispered word, ÔÇ£Lenore?ÔÇ?",

As here seems to be a real bug I would like to see more documentation in this PR, meaning an error log / message. Can you provide one (or is mine a copy of it?)

Especially: Why now? I had the issues on May 1st, but after then never again and obviously nobody else since you got them now? I can't don't want to believe we are the only two win users.

[NPException]

@Bukama yes I guess I could have included the error message in the description. 🙈 I'll edit it in.
Here it is as well:

ReportEntryExtensionTests.java:377: error: unmappable character (0x9D) for encoding windows-1252
	"And the only word there spoken was the whispered word, “Lenore?�?",

It's the same as yours, just complaining about a different encoding.

[Bukama]

Thank you for adding the information. I'll merge this PR.