book: re-render to add the redirects

I just fixed the `update-book2.rb` script so that URLs like
https://git-scm.com/book/ (with a trailing slash) redirect again; This
commit reflects the impact on the automatically rendered content files
in `external/book/`.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

external/book/content/book/az/v2/_index.html

@@ -13,4 +13,5 @@
 url: "/book/az/v2.html"
 aliases:
 - "/book/az/v2/index.html"
+- "/book/az/index.html"
 ---

external/book/content/book/be/v2/_index.html

@@ -13,4 +13,5 @@
 url: "/book/be/v2.html"
 aliases:
 - "/book/be/v2/index.html"
+- "/book/be/index.html"
 ---

external/book/content/book/bg/v2/_index.html

@@ -13,4 +13,5 @@
 url: "/book/bg/v2.html"
 aliases:
 - "/book/bg/v2/index.html"
+- "/book/bg/index.html"
 ---

external/book/content/book/cs/v2/_index.html

@@ -13,4 +13,5 @@
 url: "/book/cs/v2.html"
 aliases:
 - "/book/cs/v2/index.html"
+- "/book/cs/index.html"
 ---

external/book/content/book/de/v2/_index.html

@@ -13,4 +13,5 @@
 url: "/book/de/v2.html"
 aliases:
 - "/book/de/v2/index.html"
+- "/book/de/index.html"
 ---

external/book/content/book/en/v2/_index.html

@@ -16,4 +16,6 @@
 url: "/book/en/v2.html"
 aliases:
 - "/book/en/v2/index.html"
+- "/book/en/index.html"
+- "/book/index.html"
 ---

external/book/content/book/es/v2/_index.html

@@ -13,4 +13,5 @@
 url: "/book/es/v2.html"
 aliases:
 - "/book/es/v2/index.html"
+- "/book/es/index.html"
 ---

external/book/content/book/fa/v2/_index.html

@@ -13,4 +13,5 @@
 url: "/book/fa/v2.html"
 aliases:
 - "/book/fa/v2/index.html"
+- "/book/fa/index.html"
 ---

external/book/content/book/fr/v2/_index.html

@@ -13,4 +13,5 @@
 url: "/book/fr/v2.html"
 aliases:
 - "/book/fr/v2/index.html"
+- "/book/fr/index.html"
 ---

external/book/content/book/gr/v2/_index.html

@@ -13,4 +13,5 @@
 url: "/book/gr/v2.html"
 aliases:
 - "/book/gr/v2/index.html"
+- "/book/gr/index.html"
 ---