Quick Documentation Action

Many of stdlib functions in Lama documented by comments on previous lines
E.g
```
-- Creates a buffer from a list x
public fun listBuffer (x) {
...
}
```

But for now no documentation provided on QuickDoc Action (`ctrl+q`, `F1`)

So, need to implement this.
See `com.intellij.lang.documentation.DocumentationProviderEx`
[Official documentation](https://plugins.jetbrains.com/docs/intellij/documentation-provider.html#ensure-that-the-correct-psi-element-is-used)

Start with the IntelliJ DocumentationProviderEx API and its official documentation, then trace how the QuickDoc actions (Ctrl+Q and F1) select elements in the Lama plugin. The work is done when comments placed before stdlib functions, such as listBuffer, are shown through QuickDoc.

Written by the indexing model from the issue text.