Fix doc links

`installation.md` was not being included due to using `-` instead of `*`
in `SUMMARY.md`.  The usage link was just incorrect.

docs/src/SUMMARY.md

@@ -1,7 +1,7 @@
 # Summary
 
 - [Welcome to TaskChampion](./welcome.md)
-  - [Installation](./installation.md)
+  * [Installation](./installation.md)
   * [Using the Task Command](./using-task-command.md)
     * [Configuration](./config-file.md)
     * [Reports](./reports.md)
@@ -10,11 +10,11 @@
   * [Running the Sync Server](./running-sync-server.md)
   * [Debugging](./debugging.md)
 - [Internal Details](./internals.md)
-  - [Data Model](./data-model.md)
-    - [Replica Storage](./storage.md)
-    - [Task Database](./taskdb.md)
-    - [Tasks](./tasks.md)
-  - [Synchronization and the Sync Server](./sync.md)
-    - [Synchronization Model](./sync-model.md)
-    - [Server-Replica Protocol](./sync-protocol.md)
-    - [Planned Functionality](./plans.md)
+  * [Data Model](./data-model.md)
+    * [Replica Storage](./storage.md)
+    * [Task Database](./taskdb.md)
+    * [Tasks](./tasks.md)
+  * [Synchronization and the Sync Server](./sync.md)
+    * [Synchronization Model](./sync-model.md)
+    * [Server-Replica Protocol](./sync-protocol.md)
+    * [Planned Functionality](./plans.md)

docs/src/welcome.md

@@ -60,4 +60,4 @@ server_origin: "https://taskchampion.example.com"
 The next run of `task sync` will upload your task history to that server.
 Configuring another device identically and running `task sync` will download that task history, and continue to stay in sync with subsequent runs of the command.
 
-See [Usage](./usage.md) for more detailed information on using TaskChampion.
+See [Usage](./using-task-command.md) for more detailed information on using TaskChampion.