move metadata from README files to "epub-metadata.yml"

README-ja.md

@@ -1,10 +1,3 @@
----
-title: System Design Primer
-creator: Donne Martin
-date: 2018
-lang: ja
----
-
 *[English](README.md) ∙ [简体中文](README-zh-Hans.md) | [Brazilian Portuguese](https://github.com/donnemartin/system-design-primer/issues/40) ∙ [Polish](https://github.com/donnemartin/system-design-primer/issues/68) ∙ [Russian](https://github.com/donnemartin/system-design-primer/issues/87) ∙ [Turkish](https://github.com/donnemartin/system-design-primer/issues/39) | [Add Translation](https://github.com/donnemartin/system-design-primer/issues/28)*
 
 # システム設計入門

README-zh-Hans.md

@@ -1,10 +1,3 @@
----
-title: System Design Primer
-creator: Donne Martin
-date: 2018
-lang: zh-Hans
----
-
 > * 原文地址：[github.com/donnemartin/system-design-primer](https://github.com/donnemartin/system-design-primer)
 > * 译文出自：[掘金翻译计划](https://github.com/xitu/gold-miner)
 > * 译者：[XatMassacrE](https://github.com/XatMassacrE)、[L9m](https://github.com/L9m)、[Airmacho](https://github.com/Airmacho)、[xiaoyusilen](https://github.com/xiaoyusilen)、[jifaxu](https://github.com/jifaxu)

README-zh-TW.md

@@ -1,10 +1,3 @@
----
-title: System Design Primer
-creator: Donne Martin
-date: 2018
-lang: zh-TW
----
-
 *[English](README.md) ∙ [日本語](README-ja.md) ∙ [简体中文](README-zh-Hans.md) ∙ [繁體中文](README-zh-TW.md) | [Brazilian Portuguese](https://github.com/donnemartin/system-design-primer/issues/40) ∙ [Italian](https://github.com/donnemartin/system-design-primer/issues/104) ∙ [Korean](https://github.com/donnemartin/system-design-primer/issues/102) ∙ [Persian](https://github.com/donnemartin/system-design-primer/issues/110) ∙ [Polish](https://github.com/donnemartin/system-design-primer/issues/68) ∙ [Russian](https://github.com/donnemartin/system-design-primer/issues/87) ∙ [Turkish](https://github.com/donnemartin/system-design-primer/issues/39) ∙ [Vietnamese](https://github.com/donnemartin/system-design-primer/issues/127) | [Add Translation](https://github.com/donnemartin/system-design-primer/issues/28)*
 
 # 系統設計入門

README.md

@@ -1,10 +1,3 @@
----
-title: System Design Primer
-creator: Donne Martin
-date: 2018
-lang: en
----
-
 *[English](README.md) ∙ [日本語](README-ja.md) ∙ [简体中文](README-zh-Hans.md) ∙ [繁體中文](README-zh-TW.md) | [العَرَبِيَّة‎](https://github.com/donnemartin/system-design-primer/issues/170) ∙ [বাংলা](https://github.com/donnemartin/system-design-primer/issues/220) ∙ [Português do Brasil](https://github.com/donnemartin/system-design-primer/issues/40) ∙ [Deutsch](https://github.com/donnemartin/system-design-primer/issues/186) ∙ [ελληνικά](https://github.com/donnemartin/system-design-primer/issues/130) ∙ [Italiano](https://github.com/donnemartin/system-design-primer/issues/104) ∙ [韓國語](https://github.com/donnemartin/system-design-primer/issues/102) ∙ [فارسی](https://github.com/donnemartin/system-design-primer/issues/110) ∙ [Polski](https://github.com/donnemartin/system-design-primer/issues/68) ∙ [русский язык](https://github.com/donnemartin/system-design-primer/issues/87) ∙ [Español](https://github.com/donnemartin/system-design-primer/issues/136) ∙ [ภาษาไทย](https://github.com/donnemartin/system-design-primer/issues/187) ∙ [Türkçe](https://github.com/donnemartin/system-design-primer/issues/39) ∙ [tiếng Việt](https://github.com/donnemartin/system-design-primer/issues/127) ∙ [Français](https://github.com/donnemartin/system-design-primer/issues/250) | [Add Translation](https://github.com/donnemartin/system-design-primer/issues/28)*
 
 # The System Design Primer

epub-metadata.yaml

@@ -0,0 +1,3 @@
+title: System Design Primer
+creator: Donne Martin
+date: 2018

generate-epub.sh

@@ -13,7 +13,7 @@ generate_with_solutions () {
     : [[ -d "$dir" ]] && ( cd "$dir" && cat ./README.md >> $tmpfile && echo "" >> $tmpfile )
   done
 
-  cat $tmpfile | pandoc --from=markdown -o README.epub
+  cat $tmpfile | pandoc --metadata-file=epub-metadata.yaml --metadata=lang:en --from=markdown -o README.epub
 
   rm "$tmpfile"
 
@@ -22,12 +22,20 @@ generate_with_solutions () {
 
 generate () {
   name=$1
+  language=$2
+
   echo "Generating Ebook $name ..."
-  pandoc -o $name.epub $name.md
+
+  pandoc \
+    --metadata-file=epub-metadata.yaml \
+    --metadata=lang:$language \
+    -o $name.epub \
+    $name.md
+
   echo "Done! You can find the book at ./$name.epub"
 }
 
 generate_with_solutions
-generate README-ja
+generate README-ja ja
-generate README-zh-Hans
+generate README-zh-Hans zh-Hans
-generate README-zh-TW
+generate README-zh-TW zh-TW