use updated mdbook from upstream pr

rust-lang/mdBook#1306 (comment)

Author: Nutomic

.drone.yml

@@ -11,6 +11,6 @@ steps:
   - name: check documentation build
     image: rust:1.49-slim-buster
     commands:
-      - cargo install mdbook --git https://github.com/Nutomic/mdBook.git --branch localization
-            --rev 0982a82 --force --debug
+      - cargo install mdbook --git https://github.com/Ruin0x11/mdBook.git --branch localization
+            --rev 9d8147c --force --debug
       - mdbook build .

README.md

@@ -10,7 +10,7 @@ Our documentation tool [mdbook](https://github.com/rust-lang/mdBook) doesn't sup
 
 ```bash
 cargo install mdbook --git https://github.com/Ruin0x11/mdBook.git \
-    --branch localization --rev d06249b
+    --branch localization --rev 9d8147c
 # generate static page in `book` subfolder
 mdbook build
 # serve the book at `http://localhost:3000`, and rebuilds on changes