Fix size calculation and update build configuration

Corrected the `size` property in `SlicedByteArray` to account for offset. Bumped the version to 0.2.7 and added a custom Maven repository to the build script. Adjusted the `settings.gradle.kts` file to clean up formatting.

src/commonMain/kotlin/nl/astraeus/tba/SlicedByteArray.kt

@@ -6,7 +6,7 @@ class SlicedByteArray(
   val length: Int
 ) {
   val size: Int
-    get() = length
+    get() = length - offset
 
   constructor(array: ByteArray) : this(array, 0, array.size)