Support webMain source set

[rjaros]

When using webMain shared JS/WasmJS source set, the Gradle plugin doesn't automatically add directory with generated sources to the compilation.

[rjaros]

There are also some problems with tasks dependencies, I think also caused by webMain source set:

A problem was found with the configuration of task ':back:kspKotlinJs' (type 'KspAATask').
  - Gradle detected a problem with the following location: '/home/rjaros/git/finn/eizba/back/build/ktml/webMain'.
    
    Reason: Task ':back:kspKotlinJs' uses this output of task ':back:generateKtml' without declaring an explicit or implicit dependency. This can lead to incorrect results being produced, depending on what order the tasks are executed.
    
    Possible solutions:
      1. Declare task ':back:generateKtml' as an input of ':back:kspKotlinJs'.
      2. Declare an explicit dependency on ':back:generateKtml' from ':back:kspKotlinJs' using Task#dependsOn.
      3. Declare an explicit dependency on ':back:generateKtml' from ':back:kspKotlinJs' using Task#mustRunAfter.
    
    For more information, please refer to https://docs.gradle.org/9.2.1/userguide/validation_problems.html#implicit_dependency in the Gradle documentation.

* Try:
> Declare task ':back:generateKtml' as an input of ':back:kspKotlinJs'
> Declare an explicit dependency on ':back:generateKtml' from ':back:kspKotlinJs' using Task#dependsOn
> Declare an explicit dependency on ':back:generateKtml' from ':back:kspKotlinJs' using Task#mustRunAfter

[rjaros]

I use something like this as a workaround:

kotlin {
    sourceSets {
        val webMain by getting {
            dependencies {
            kotlin.srcDir("build/ktml/webMain")
        }
    }
}
afterEvaluate {
    tasks {
        getByName("kspKotlinJs") {
            dependsOn("generateKtml")
        }
        getByName("kspKotlinWasmJs") {
            dependsOn("generateKtml")
        }
    }
}