Add "source" button to API docs

[SebastianAigner]

Currently, there is no convenient way to navigate from the API docs to the actual code in the repository.

Compare other libraries, where Dokka links to the actual source / implementation of symbols: https://hoc081098.github.io/FlowExt/docs/0.x/-flow-ext/com.hoc081098.flowext/-delay-strategy/index.html

This makes it harder for people who might want to contribute documentation improvements, clarifications, and the like. It'd be great if the button could be added!

[dkhalanskyjb]

Here's the API reference for this library: https://kotlinlang.org/api/kotlinx.coroutines/

Here's an example of the page from that API reference: https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/async.html

For me, the (source) button renders and works appropriately.

[whyoleg]

@dkhalanskyjb take a look on modules other then core:

• test - https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-test/kotlinx.coroutines.test/run-test.html
• reactive - https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-reactive/kotlinx.coroutines.reactive/as-flow.html

On current moment kotlinx-coroutines configure Dokka sourceLinks only for core:

kotlinx.coroutines/gradle/dokka.gradle.kts

Line 48 in ecb5b3e

if (project.name == "kotlinx-coroutines-core") {