feat(builder): added IsBase64Builder

Author: ziccardi

src/rules/RuleBuilder.ts

@@ -4,6 +4,7 @@ import {builder as CompositeRuleBuilder} from './builders/CompositeRuleBuilder';
 import {builder as RequiredRuleBuilder} from './builders/RequiredValueBuilder';
 import {builder as LengthRuleBuilder} from './builders/LengthRuleBuilder';
 import {builder as MatchesRuleBuilder} from './builders/MatchesRuleBuilder';
+import {builder as IsBase64Builder} from './builders/IsBase64Builder';
 
 // tslint:disable-next-line:variable-name
 export const RuleBuilder = {
@@ -13,4 +14,5 @@ export const RuleBuilder = {
   required: RequiredRuleBuilder.required,
   length: LengthRuleBuilder,
   matches: MatchesRuleBuilder.withPattern,
+  isBase64: IsBase64Builder,
 };

src/rules/builders/IsBase64Builder.ts

@@ -0,0 +1,19 @@
+import {RuleConfig} from '../../config/RuleConfig';
+
+export interface IsBase64BuilderWithPathBuilder {
+  build: () => RuleConfig;
+}
+
+export interface IsBase64InitialBuilder extends IsBase64BuilderWithPathBuilder {
+  withPath: (path: string) => IsBase64BuilderWithPathBuilder;
+}
+
+export const builder: IsBase64InitialBuilder = {
+  withPath: (path: string): IsBase64BuilderWithPathBuilder => {
+    const rule = {type: 'isBase64', path};
+    return {
+      build: () => rule,
+    };
+  },
+  build: (): RuleConfig => ({type: 'isBase64'}),
+};