docs: document changes to ls output and new regex filter feat

README.md

@@ -106,7 +106,7 @@ fisher add ~/path/to/local/pkg
 
 ### Listing packages
 
-List all the packages that are currently installed using the `ls` command. This includes packages you didn't install yourself but were installed on your system as a dependency of another package.
+List all the packages that are currently installed using the `ls` command. This shows only the packages that you've installed yourself, ignoring their dependencies.
 
 ```
 fisher ls
@@ -117,6 +117,12 @@ edc/bass
 ~/path/to/myfish/pkg
 ```
 
+Is the output too large? This command accepts a regular expression to filter the listed packages.
+
+```
+fisher ls "^gitlab|fish-.*"
+```
+
 ### Removing packages
 
 Remove packages using the `rm` command. If a package has dependencies, they too will be removed. If any dependencies are still shared by other packages, they will remain installed.