Add tests for nested unordered and checkbox lists, extend parser for indentation handling, and bump version to 2.0.0

src/commonMain/kotlin/nl/astraeus/markdown/parser/Markdown.kt

@@ -1,9 +1,16 @@
 package nl.astraeus.markdown.parser
 
+data class ListItem(
+  val text: String,
+  val order: Int,
+  val indentation: Int = 0
+)
+
 data class CheckboxItem(
   val line: Int,
   val checked: Boolean,
   val text: String,
+  val indentation: Int = 0
 )
 
 sealed class MarkdownPart {
@@ -66,7 +73,7 @@ sealed class MarkdownPart {
   ) : MarkdownPart()
 
   data class UnorderedList(
-    val lines: List<Pair<Int, String>>,
+    val lines: List<ListItem>,
   ) : MarkdownPart()
 
   data class CheckboxList(
@@ -74,7 +81,7 @@ sealed class MarkdownPart {
   ) : MarkdownPart()
 
   data class OrderedList(
-    val lines: List<String>,
+    val lines: List<ListItem>,
   ) : MarkdownPart()
 
   data class CodeBlock(