Propose apk

Reviewed-by: Ariadne Conill <ariadne@dereferenced.org>
Signed-off-by: Morten Linderud <morten@linderud.pw>

PURL-TYPES.rst

@@ -23,6 +23,24 @@ See also https://github.com/package-url/purl-spec and
 Known ``purl`` types
 ~~~~~~~~~~~~~~~~~~~~
 
+apk
+---
+``apk`` for APK-based packages:
+
+- There is no default package repository: this should be implied either from
+  the ``distro`` qualifiers key  or using a repository base url as 
+  ``repository_url`` qualifiers key.
+- The ``namespace`` is the vendor such as ``alpine`` or ``openwrt``. It is not
+  case sensitive and must be lowercased.
+- The ``name`` is the package name. It is not case sensitive and must be
+  lowercased.
+- The ``version`` is a package version as expected by apk.
+- The ``arch`` is the qualifiers key for a package architecture.
+- Examples::
+
+      pkg:apk/alpine/curl@7.83.0-r0?arch=x86
+      pkg:apk/alpine/apk@2.12.9-r3?arch=x86
+
 bitbucket
 ---------
 ``bitbucket`` for Bitbucket-based packages:
@@ -390,7 +408,6 @@ swift
 Other candidate types to define:
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-- ``alpine`` for Alpine Linux apk packages:
 - ``apache`` for Apache projects packages:
 - ``android`` for Android apk packages:
 - ``arch`` for Arch Linux packages: