fix: builds should no accumulate on repeated changes (closes #404)

Jacky Zhao

2023-08-23 a1a1e7e1e0c06f2f7b759c5aecd6a9ceba3e2717

 quartz/plugins/transformers/frontmatter.ts

@@ -41,7 +41,7 @@
            }

            // slug them all!!
            data.tags = data.tags?.map((tag: string) => slugTag(tag)) ?? []
            data.tags = [...new Set(data.tags?.map((tag: string) => slugTag(tag)))] ?? []

            // fill in frontmatter
            file.data.frontmatter = {