Add documentation and reorder methods alphabetically in purl-type.ts

Improves code organization and documentation:
- Add JSDoc comments for PurlTypNormalizer and PurlTypeValidator constants
- Reorder helper functions alphabetically (create*, getNpm*, isNpm*)

The alphabetic ordering groups related functions together and makes
them easier to locate when navigating the file.

Author: jdalton

src/purl-type.ts

@@ -25,9 +25,39 @@ interface PurlObject {
   version?: string
 }
 
+/**
+ * Default normalizer for PURL types without specific normalization rules.
+ */
 const PurlTypNormalizer = (purl: PurlObject): PurlObject => purl
+
+/**
+ * Default validator for PURL types without specific validation rules.
+ */
 const PurlTypeValidator = (_purl: PurlObject, _throws: boolean): boolean => true
 
+/**
+ * Create normalizer that only lowercases name.
+ */
+function createLowerNameNormalizer(): (_purl: PurlObject) => PurlObject {
+  return (purl: PurlObject) => {
+    lowerName(purl)
+    return purl
+  }
+}
+
+/**
+ * Create normalizer that lowercases both namespace and name.
+ */
+function createLowerNamespaceAndNameNormalizer(): (
+  _purl: PurlObject,
+) => PurlObject {
+  return (purl: PurlObject) => {
+    lowerNamespace(purl)
+    lowerName(purl)
+    return purl
+  }
+}
+
 /**
  * Get list of Node.js built-in module names.
  */
@@ -94,6 +124,14 @@ const getNpmBuiltinNames = (() => {
   }
 })()
 
+/**
+ * Get npm package identifier with optional namespace.
+ */
+function getNpmId(purl: PurlObject): string {
+  const { name, namespace } = purl
+  return `${namespace && namespace.length > 0 ? `${namespace}/` : ''}${name}`
+}
+
 /**
  * Get list of npm legacy package names.
  */
@@ -127,14 +165,6 @@ const getNpmLegacyNames = (() => {
   }
 })()
 
-/**
- * Get npm package identifier with optional namespace.
- */
-function getNpmId(purl: PurlObject): string {
-  const { name, namespace } = purl
-  return `${namespace && namespace.length > 0 ? `${namespace}/` : ''}${name}`
-}
-
 /**
  * Check if npm identifier is a built-in module name.
  */
@@ -147,29 +177,6 @@ const isNpmBuiltinName = (id: string): boolean =>
 const isNpmLegacyName = (id: string): boolean =>
   getNpmLegacyNames().includes(id)
 
-/**
- * Create normalizer that lowercases both namespace and name.
- */
-function createLowerNamespaceAndNameNormalizer(): (
-  _purl: PurlObject,
-) => PurlObject {
-  return (purl: PurlObject) => {
-    lowerNamespace(purl)
-    lowerName(purl)
-    return purl
-  }
-}
-
-/**
- * Create normalizer that only lowercases name.
- */
-function createLowerNameNormalizer(): (_purl: PurlObject) => PurlObject {
-  return (purl: PurlObject) => {
-    lowerName(purl)
-    return purl
-  }
-}
-
 // PURL types:
 // https://github.com/package-url/purl-spec/blob/master/PURL-TYPES.rst
 const PurlType = createHelpersNamespaceObject(