change to contentlayer2 and update dependencies

contentlayer.config.ts

@@ -1,4 +1,4 @@
-import { defineDocumentType, ComputedFields, makeSource } from 'contentlayer/source-files'
+import { defineDocumentType, ComputedFields, makeSource } from 'contentlayer2/source-files'
 import { writeFileSync } from 'fs'
 import readingTime from 'reading-time'
 import { slug } from 'github-slugger'
@@ -134,6 +134,7 @@ export default makeSource({
   mdx: {
     cwd: process.cwd(),
     remarkPlugins: [
+      // @ts-ignore
       remarkExtractFrontmatter,
       remarkGfm,
       remarkCodeTitles,