add Base64 handling

ts/smartstring.base64.ts

@@ -0,0 +1,46 @@
+import * as plugins from './smartstring.plugins'
+
+/**
+ * the type for base 64
+ */
+export type TBase64Input = 'string' | 'base64' | 'base64uri'
+
+/**
+ * handle base64 strings
+ */
+export class Base64 {
+    private refString: string
+    constructor(inputStringArg, typeArg: TBase64Input) {
+        switch (typeArg) {
+            case 'string': // easiest case
+                this.refString = inputStringArg
+                break
+            case 'base64':
+                this.refString = plugins.jsBase64.decode(inputStringArg)
+                break
+            case 'base64uri':
+                this.refString = plugins.jsBase64.decode(inputStringArg)
+        }
+    }
+
+    /**
+     * the simple string (unencoded)
+     */
+    get simpleString() {
+        return this.refString
+    }
+
+    /**
+     * the base64 encoded version of the original string
+     */
+    get base64String() {
+        return plugins.jsBase64.encode(this.refString)
+    }
+
+    /**
+     * the base64uri encoded version of the original string
+     */
+    get base64StringUri() {
+        return plugins.jsBase64.encodeURI(this.refString)
+    }
+}