Make watermarker library usable as JavaScript library

One possible (but maybe not the most elegant) solution is to use the @JsExport annotation that can be imported using import kotlin.js.JsExport. Find more information here. As this annotation is currently still experimental, it has to be opted in and used like follows:

import kotlin.js.JsExport
...
@OptIn(kotlin.js.ExperimentalJsExport::class)
@JsExport
class TextWatermark private constructor(
    content: List<Byte>,
    private val compression: Boolean,
) : Watermark(content) {
    /** Returns the uncompressed bytes from the Watermark */
    fun getBytes(): Result<List<Byte>> {
        return if (compression) {
            Compression.inflate(content)
        } else {
            Result.success(content)
        }
    }
[](url)
    /** Parses the uncompressed bytes as String */
    fun getText(): Result<String> {
    ...

There are a few things to be mentioned here:

As JS does not support function overloading, the @JsName("[FunctionName]") annotation has to be used for overloaded functions like those in the Result class.
```
/** Creates a new Result<T> from [status] and [value] */
@JsName("intoResult")
fun <T> into(value: T? = null) = Result(this.status, value)
```

/* Converts Result to Status / @JsName("intoStatus") fun into(): Status = this.status

More information can be found [here](https://kotlinlang.org/docs/js-to-kotlin-interop.html#jsname-annotation).

2. For the generation of JS code to work, the `build.gradle.kts` file has to be adapted like follows:

kotlin { ... js(IR) { browser { } binaries.executable() } ... }


More information can be found [here](https://kotlinlang.org/docs/js-project-setup.html#execution-environments).

3. When everything is configurated correctly, the JS code can be generated using `.\gradlew build`. By default, the source code will be placed in the `./build/js/packages/watermarker/kotlin/` directory. A minified version will be placed in the `./build/dist/js/productionExecutable/` directory.

4. I have not yet been able to investigate, whether the `@JsExport` annotation has to be used for every class, or if dependencies can be resolved automatically.

5. There might be more elegant options to generate JS code from kotlin that I am currently unaware of.

FraunhoferISST / TREND

Make watermarker library usable as JavaScript library #24

🚀 Feature Request

Current Problem

Proposed Solution

Additional Context