more doc

README.md

@@ -31,5 +31,28 @@ ln -s /etc/nginx/sites-available/groff-web.conf /etc/nginx/sites-enabled
 systemctl reload nginx
 ```
 
+## Configuration
+
+These are included in the `public/compiler.sh` file, the binaries' PATH can
+be modified in case you want to compile groff from source, for example.
+As for the preprocessors, `grap` isn't installed by default in most systems,
+so you might want to remove the `G`, also `chem` gives me a bit of trouble
+when used with `eqn`.
+
+```shell
+SOELIM="/usr/bin/soelim"     # soelim PATH
+REFER="/usr/bin/refer"       # refer PATH
+GROFF="/usr/bin/groff"       # groff PATH
+PRE="-ketpG"                 # Preprocessors
+```
+
+These are not set, but you can set them if you want a directory with macros,
+or a custom bibliography file.
+
+```shell
+BIB="bibliography" # Bibliography file
+MAC="macros"       # Macros dir
+```
+
 ## License
 GPL v3.0