feat: add four new cover images

src/content/journal/2007/japanese-colors.mdx

@@ -4,6 +4,7 @@ slug: japanese-colors
 author: Stefan Imhoff
 date: 2007-12-08
 description: Traditional, Japanese colors as a color palette for Photoshop and Illustrator to download (FREE).
+cover: /assets/images/cover/japanese-colors.webp
 tags: ["design", "download", "book", "recommendation"]
 ---
 

src/content/journal/2014/website-typography.mdx

@@ -4,6 +4,7 @@ slug: website-typography
 author: Stefan Imhoff
 date: 2014-06-19
 description: "About the typography of my new website: scale, font, vertical rhythm, font size, font size, and sentence width."
+cover: /assets/images/cover/website-typography.webp
 tags: ["design", "code", "book"]
 ---
 

src/content/journal/2017/minimalism.mdx

@@ -5,6 +5,7 @@ author: Stefan Imhoff
 date: 2017-06-07
 featured: true
 description: Minimalism is currently popular, but Minimalism is hard to understand, and many misconceptions can be found. This essay carries my thoughts on Minimalism and my history with it.
+cover: /assets/images/cover/minimalism.webp
 tags: ["self-improvement", "book"]
 ---
 

src/content/journal/2021/learning-poems.mdx

@@ -4,6 +4,7 @@ slug: learning-poems
 date: 2021-08-23
 author: Stefan Imhoff
 description: Why I started learning poems.
+cover: /assets/images/cover/learning-poems.webp
 tags: ["poetry", "self-improvement", "book"]
 ---