Highlight that the path in niri.service should be checked (#962)

* Highlight that the path in niri.service should be checked

Having just installed niri I ran into this issue.  When building from source on Ubuntu the install location using the instructions in this document is /usr/local//bin/niri.

However niri.service pointed to /usr/bin/niri so my session would not start at all. Hopefully this update helps

* Update wiki/Getting-Started.md

---------

Co-authored-by: Ivan Molodetskikh <[email protected]>

Author: mrheinen

wiki/Getting-Started.md

@@ -166,6 +166,9 @@ If installing directly without a package, the recommended file destinations are
 In this case, put the files in the directories indicated in the table below.
 These may vary depending on your distribution.
 
+Don't forget to make sure that the path to `niri` in niri.service is correct.
+This defaults to `/usr/bin/niri`.
+
 | File | Destination |
 | ---- | ----------- |
 | `target/release/niri` | `/usr/local/bin/` |