Change docs links to actual file extension (.md)

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

Change-Id: Id9dfcd79704d1315d646b800c82c3b5818416836
diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
index bb91d0e..e5ad4c7 100644
--- a/src/main/resources/Documentation/about.md
+++ b/src/main/resources/Documentation/about.md
@@ -6,15 +6,15 @@
 in Jenkins. A service user is not able to login into the Gerrit WebUI
 and it cannot push commits or tags.
 
-This plugin supports the creation of service users via [SSH](cmd-create.html),
-[REST](rest-api-config.html) and in the [WebUI](#webui).
+This plugin supports the creation of service users via [SSH](cmd-create.md),
+[REST](rest-api-config.md) and in the [WebUI](#webui).
 
 To create a service user a user must be a member of a group that is
 granted the 'Create Service User' capability (provided by this plugin)
 or the 'Administrate Server' capability.
 
 The plugin can be [configured to automatically add new service users to
-groups](config.html#group). This allows to automatically assign or
+groups](config.md#group). This allows to automatically assign or
 block certain access rights for the service users.
 
 For each created service user the plugin stores some
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 8ca7754..1380b73 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -79,15 +79,15 @@
 
 Every service user for which a public SSH key is uploaded can access
 Gerrit projects via Git over SSH (if the
-[Read](access-control.html#category_read) permission is granted).
+[Read](access-control.md#category_read) permission is granted).
 
 In addition these service users can make use of the Gerrit
-[SSH API](cmd-index.html#user_commands).
+[SSH API](cmd-index.md#user_commands).
 
 E.g. this enables service users to be used for continuous integration
 builds: They can clone projects, fetch open changes and then vote and
 comment on the changes (for voting the corresponding
-[label permission](access-control.html#category_review_labels) must be
+[label permission](access-control.md#category_review_labels) must be
 assigned on the project).
 
 There is no setting to disable SSH access for service users.
@@ -95,7 +95,7 @@
 ### Git over HTTP / Access to REST API
 
 To be able to do Git operations over HTTP and to access the Gerrit
-[REST API](rest-api.html) service users must have an HTTP password.
+[REST API](rest-api.md) service users must have an HTTP password.
 
 Gerrit administrators can control by the
 [allowHttpPassword](#allowHttpPassword) plugin configuration parameter