Updated documentation.

Author: dreibh

README.md

@@ -157,6 +157,12 @@ cmake .
 make
 ```
 
+Optionally, for installation to the standard paths (usually under `/usr/local`):
+
+```bash
+sudo make install
+```
+
 Note: The script [`ci/get-dependencies`](https://github.com/dreibh/rsplib/blob/master/ci/get-dependencies) automatically  installs the build dependencies under Debian/Ubuntu Linux, Fedora Linux, and FreeBSD. For manual handling of the build dependencies, see the packaging configuration in [`debian/control`](https://github.com/dreibh/rsplib/blob/master/debian/control) (Debian/Ubuntu Linux), [`rsplib.spec`](https://github.com/dreibh/rsplib/blob/master/rpm/rsplib.spec) (Fedora Linux), and [`Makefile`](https://github.com/dreibh/rsplib/blob/master/freebsd/rsplib/Makefile) FreeBSD.
 
 Contributions: