Mention shaders in our install instructions.

If we're going to lug them around, we might as well use them.

docs/install/linux.md

@@ -72,6 +72,10 @@ as described in the previous section:
     to install icarus and its game database
  4. Type `make -C higan install` and press Enter
     to install higan and its supporting files
+ 5. If the higan source includes a `shaders` subdirectory,
+    type `make -C shaders install`
+    to install the example
+    [video shaders](../guides/shaders.md).
 
 This installs higan and its associated data files
 into the `~/.local` directory hierarchy.

docs/install/windows.md

@@ -124,6 +124,12 @@ Installing a compiled build on Windows
  5. Copy all the `*.sys` folders
     in `C:\higan-src\higan\systems`
     into the new folder
+ 6. If the higan source includes a `shaders` folder,
+    make another new folder named `Video Shaders`
+    inside the new folder,
+    and copy all the `*.shader` folders
+    from `C:\higan-src\shaders\`
+    into the `Video Shaders` folder.
 
 The new folder should now contain
 `icarus.exe`,