Refactor placeholder constants into dedicated file

Moved REPO_NAME and related constants into Placeholders.kt to improve code organization and maintainability. The code now dynamically references these constants where needed, simplifying updates and ensuring consistency across modules. Updated relevant imports and references to accommodate these changes.

src/jvmMain/kotlin/nl/astraeus/tmpl/web/Index.kt

@@ -8,6 +8,8 @@ import kotlinx.html.script
 import kotlinx.html.stream.appendHTML
 import kotlinx.html.title
 import nl.astraeus.tmpl.REPO_NAME
+import nl.astraeus.tmpl.pageTitle
+import nl.astraeus.tmpl.repoName
 
 fun generateIndex(patch: String?): String {
   val result = StringBuilder();
@@ -15,17 +17,17 @@ fun generateIndex(patch: String?): String {
   if (patch == null) {
     result.appendHTML(true).html {
       head {
-        title("${REPO_NAME}")
+        title(pageTitle)
         //link("/css/all.min.css", "stylesheet")
       }
       body {
-        script(src = "/${REPO_NAME}.js") {}
+        script(src = "/$repoName.js") {}
       }
     }
   } else {
     result.appendHTML(true).html {
       head {
-        title("${REPO_NAME}")
+        title(pageTitle)
         meta {
           httpEquiv = "refresh"
           content = "0; url=/$itemUrl/$patch"