Update Kotlin version, refine .gitignore, and optimize tests

Upgraded Kotlin Multiplatform plugin to version 2.1.20 for better compatibility and feature enhancements. Adjusted .gitignore to include `.idea/**` for broader IntelliJ configuration exclusion. Increased test iteration count in `TestCachedString` to improve benchmarking precision.

.gitignore

@@ -5,6 +5,7 @@ build/
 !**/src/test/**/build/
 
 ### IntelliJ IDEA ###
+.idea/**
 .idea/modules.xml
 .idea/jarRepositories.xml
 .idea/compiler.xml

build.gradle.kts

@@ -1,5 +1,5 @@
 plugins {
-    kotlin("multiplatform") version "2.1.0"
+    kotlin("multiplatform") version "2.1.20"
     `maven-publish`
     signing
     id("org.jetbrains.dokka") version "1.5.31"

readme.md

@@ -46,4 +46,3 @@ When such a type is updated, for example we update a string with a shorter strin
 
 Strings are stored as UTF-8 bytes, there is also a CachedStringProperty which will keep a copy of the string so it isn't converted to a 
 native string every time it's accessed.
-

src/jvmTest/kotlin/nl/astraeus/tba/TestCachedString.kt

@@ -25,7 +25,7 @@ class TestCachedString {
     notCachedPerson.name = "A Longer Longer Longer Longer Longer Test"
 
     var total = 0
-    repeat(1000000) {
+    repeat(10000000) {
       total += cachedPerson.name.hashCode()
       total += notCachedPerson.name.hashCode()
     }
@@ -34,14 +34,14 @@ class TestCachedString {
 
     var start1 = System.nanoTime()
     var total1 = 0
-    repeat(1000000) {
+    repeat(10000000) {
       total1 += cachedPerson.name.hashCode()
     }
     val stop1 = System.nanoTime()
 
     var start2 = System.nanoTime()
     var total2 = 0
-    repeat(1000000) {
+    repeat(10000000) {
       total2 += notCachedPerson.name.hashCode()
     }
     val stop2 = System.nanoTime()