Update documentation (#1103)

docs/CLI.md

@@ -8,6 +8,7 @@ Usage: marktext [commands] [path ...]
         --debug                   Enable debug mode
         --safe                    Disable plugins and other user configuration
         --dump-keyboard-layout    Dump keyboard information
+    -n, --new-window              Open a new window on second-instance
         --user-data-dir           Change the user data directory
         --disable-gpu             Disable GPU hardware acceleration
     -v, --verbose                 Be verbose

docs/PORTABLE.md

@@ -0,0 +1,14 @@
+# Portable Mode
+
+Mark Text stores all user configuration inside the [application data directory](APPLICATION_DATA_DIRECTORY.md) that can be changed with `--user-data-dir` command-line flag.
+
+## Linux and Window
+
+On Linux and Window you can also create a directory called `marktext-user-data` to save all user data inside the directory. Like:
+
+```
+marktext-portable/
+ ├── marktext/Mark Text.exe
+ ├── marktext-user-data/
+ └── ...
+```