feat(contented): add boolean PipelineField (#630)

#### What this PR does / why we need it:

Support boolean validation.

Author: fuxingloh

packages/contented-pipeline-md/src/plugins/RemarkFrontmatter.ts

@@ -92,6 +92,8 @@ export function remarkFrontmatterValidate(): Transformer<Parent> {
 
 function isTypeValid(type: string, value: any) {
   switch (type.replaceAll(' ', '')) {
+    case 'boolean':
+      return typeof value === 'boolean';
     case 'string':
       return typeof value === 'string';
     case 'number':

packages/contented-pipeline/src/PipelineField.ts

@@ -1,4 +1,5 @@
 export type PipelineField =
+  | AbstractField<'boolean', boolean>
   | AbstractField<'string', string>
   | AbstractField<'number', number>
   | AbstractField<'string[]', string[]>