[KorTE]: Add replace filter

See https://github.com/korlibs/korge/issues/955

Expected usage:

```
{{ variable | replace("\n", "
") }}
```

Filter should should be implemented here:
* https://github.com/korlibs/korge/blob/09c5f9cb5a6e0ea756b052afd661b365c07c48c1/korte/src/commonMain/kotlin/com/soywiz/korte/DefaultFilters.kt
* https://github.com/korlibs/korge/blob/09c5f9cb5a6e0ea756b052afd661b365c07c48c1/korte/src/commonTest/kotlin/com/soywiz/korte/TemplateTest.kt#L255

Start in korte/src/commonMain/kotlin/com/soywiz/korte/DefaultFilters.kt, then review the relevant cases in korte/src/commonTest/kotlin/com/soywiz/korte/TemplateTest.kt around line 255. Implement the replace filter for the shown template usage and add or update a test demonstrating that newline characters become the requested replacement text.

Written by the indexing model from the issue text.