Change docs links to actual file extension (.md)

See https://gerrit-review.googlesource.com/83950 for detailed context.

Change-Id: Iec8e8974c96df9f7849dcac92a2e623e80c7175f

src/main/resources/Documentation/about.md

diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
index 9279cb3..0ae87f3 100644
--- a/src/main/resources/Documentation/about.md
+++ b/src/main/resources/Documentation/about.md
@@ -41,12 +41,12 @@
 
 To configure an external image server the image server that comes with
 the plugin must be disabled. This is done by setting the
-[enableImageServer](config.html#enable-image-server) to `false`.
+[enableImageServer](config.md#enable-image-server) to `false`.
 
 A regular expression to match URLs of images that should be embedded
-must be configured as [pattern](config.html#pattern).
+must be configured as [pattern](config.md#pattern).
 
-Optionally also a [URL for uploading images](config.html#upload-url)
+Optionally also a [URL for uploading images](config.md#upload-url)
 can be defined.
 
 ```

src/main/resources/Documentation/rest-api-projects.md

diff --git a/src/main/resources/Documentation/rest-api-projects.md b/src/main/resources/Documentation/rest-api-projects.md
index 9e738eb..cbd7f59 100644
--- a/src/main/resources/Documentation/rest-api-projects.md
+++ b/src/main/resources/Documentation/rest-api-projects.md
@@ -22,7 +22,7 @@
 [Create Reference](../../../Documentation/access-control.html#category_create)
 access right on the `refs/images/*` namespace of the project.
 
-Only available if [image server is enabled](config.html#enable-image-server).
+Only available if [image server is enabled](config.md#enable-image-server).
 
 #### Request
 
@@ -52,7 +52,7 @@
 granted the `Delete Own Images` global capability which allows deleting
 own images.
 
-Only available if [image server is enabled](config.html#enable-image-server).
+Only available if [image server is enabled](config.md#enable-image-server).
 
 #### Request