[FEAT] Added in-code examples for document API

Public API can be documented with an external
set of test-like functions that show a a given
public package API function can be used.

Author: mdm-code

example_test.go

@@ -0,0 +1,51 @@
+package xdg_test
+
+import (
+	"fmt"
+
+	"github.com/mdm-code/xdg"
+)
+
+func ExampleDataHomeDir() {
+	dir := xdg.DataHomeDir()
+	fmt.Println("Home data directory: ", dir)
+}
+
+func ExampleConfigHomeDir() {
+	dir := xdg.ConfigHomeDir()
+	fmt.Println("Config home directory: ", dir)
+}
+
+func ExampleStateHomeDir() {
+	dir := xdg.StateHomeDir()
+	fmt.Println("State home directory: ", dir)
+}
+
+func ExampleDataDirs() {
+	dir := xdg.DataDirs()
+	fmt.Println("Data directories: ", dir)
+}
+
+func ExampleConfigDirs() {
+	dir := xdg.ConfigDirs()
+	fmt.Println("Config directories: ", dir)
+}
+
+func ExampleCacheHomeDir() {
+	dir := xdg.CacheHomeDir()
+	fmt.Println("Cache home directory: ", dir)
+}
+
+func ExampleRuntimeDir() {
+	dir := xdg.RuntimeDir()
+	fmt.Println("Runtime home directory: ", dir)
+}
+
+func ExampleFind() {
+	fpath := "program/file.data"
+	if f, ok := xdg.Find(xdg.Data, fpath); ok {
+		fmt.Printf("Data file for %s was found at %s\n", fpath, f)
+	} else {
+		fmt.Printf("ERROR: couldn't find %s\n", fpath)
+	}
+}