Init for korean docs (#1910)

* init for korean docs

* edit build yml file for multi language docs

* edit one more build yml file for multi language docs

* add title for get_frontmatter error

.github/workflows/build_documentation.yml

@@ -13,5 +13,6 @@ jobs:
     with:
       commit_sha: ${{ github.sha }}
       package: diffusers
+      languages: en ko
     secrets:
       token: ${{ secrets.HUGGINGFACE_PUSH }}

.github/workflows/build_pr_documentation.yml

@@ -14,3 +14,4 @@ jobs:
       commit_sha: ${{ github.event.pull_request.head.sha }}
       pr_number: ${{ github.event.number }}
       package: diffusers
+      languages: en ko