Move pandoc/ folder out of the way (#1704)

The config fragments there are only used in the GitHub actions, so we
can stash them way in the `.github/` folder.

.github/pandoc/README.md

@@ -0,0 +1,4 @@
+# Config Overrides for `mdbook-pandoc`
+
+The configuration file fragments here are used to override the configuration in
+`book.toml`. See `.github/workflows/build.sh` for details.

.github/pandoc/ja.yaml

@@ -0,0 +1,4 @@
+variables:
+  CJKmainfont: "Noto Serif CJK JP"
+  CJKsansfont: "Noto Sans CJK JP"
+  CJKmonofont: "Noto Sans Mono CJK JP"

.github/pandoc/ko.yaml

@@ -0,0 +1,4 @@
+variables:
+  CJKmainfont: "Noto Serif CJK KR"
+  CJKsansfont: "Noto Sans CJK KR"
+  CJKmonofont: "Noto Sans Mono CJK KR"

.github/pandoc/zh-CN.yaml

@@ -0,0 +1,4 @@
+variables:
+  CJKmainfont: "Noto Serif CJK SC"
+  CJKsansfont: "Noto Sans CJK SC"
+  CJKmonofont: "Noto Sans Mono CJK SC"

.github/pandoc/zh-TW.yaml

@@ -0,0 +1,4 @@
+variables:
+  CJKmainfont: "Noto Serif CJK TC"
+  CJKsansfont: "Noto Sans CJK TC"
+  CJKmonofont: "Noto Sans Mono CJK TC"

.github/workflows/build.sh

@@ -31,11 +31,15 @@ else
     export MDBOOK_OUTPUT__HTML__REDIRECT='{}'
 
     # Include language-specific Pandoc configuration
-    [ -f "pandoc/$book_lang.yaml" ] && export MDBOOK_OUTPUT__PANDOC__PROFILE__PDF__DEFAULTS="pandoc/$book_lang.yaml"
+    if [ -f ".github/pandoc/$book_lang.yaml" ]; then
+        export MDBOOK_OUTPUT__PANDOC__PROFILE__PDF__DEFAULTS=".github/pandoc/$book_lang.yaml"
+    fi
 fi
 
 mdbook build -d "$dest_dir"
-[ -f "$dest_dir/pandoc/pdf/comprehensive-rust.pdf" ] && mv "$dest_dir/pandoc/pdf/comprehensive-rust.pdf" "$dest_dir/html/"
+if [ -f "$dest_dir/pandoc/pdf/comprehensive-rust.pdf" ]; then
+    mv "$dest_dir/pandoc/pdf/comprehensive-rust.pdf" "$dest_dir/html/"
+fi
 (cd "$dest_dir/exerciser" && zip --recurse-paths ../html/comprehensive-rust-exercises.zip comprehensive-rust-exercises/)
 
 echo "::endgroup::"