docs: add README, per-resource examples, unit tests, CI, and pre-commit

- Add README.md with provider docs, resource/data-source reference, and
  development instructions
- Reorganize examples into per-resource-type subdirectories following
  Terraform provider conventions, add missing pypi/npm/puppet examples
- Add unit tests for helpers, HTTP client, model conversions, and
  provider registration
- Add Woodpecker CI pipelines for lint, test, and build
- Add pre-commit config with standard and Go-specific hooks

examples/data-sources/artifactapi_virtual/main.tf

@@ -0,0 +1,26 @@
+terraform {
+  required_providers {
+    artifactapi = {
+      source  = "git.unkin.net/unkin/artifactapi"
+      version = "0.0.1"
+    }
+  }
+}
+
+provider "artifactapi" {
+  endpoint = "https://artifactapi.example.com"
+}
+
+# Read the configuration of an existing virtual repository by name.
+# Returns the package type, description, and ordered member list.
+data "artifactapi_virtual" "helm" {
+  name = "helm"
+}
+
+output "helm_members" {
+  value = data.artifactapi_virtual.helm.members
+}
+
+output "helm_package_type" {
+  value = data.artifactapi_virtual.helm.package_type
+}