Rename `dir_permissions` segment to `dir_writable`

Additionally:
- Add changelog entry
- Add documentation

CHANGELOG.md

@@ -20,6 +20,10 @@ Added an option to configure the path separator. If you want something
 else than an ordinary slash, you could set
 `POWERLEVEL9K_DIR_PATH_SEPARATOR` to whatever you want.
 
+### New segment 'dir_writable' added
+
+This segment displays a lock icon if your user has no write permissions in the current folder.
+
 ### New segment 'disk_usage' added
 
 This segment will show the usage level of your current partition.

README.md

@@ -89,6 +89,7 @@ The segments that are currently available are:
 * [`battery`](#battery) - Current battery status.
 * [`context`](#context) - Your username and host.
 * [`dir`](#dir) - Your current working directory.
+* `dir_writable` - Displays a lock icon, if you do not have write permissions on the current folder.
 * [`disk_usage`](#disk_usage) - Disk usage of your current partition.
 * `history` - The command number for the current line.
 * [`ip`](#ip) - Shows the current IP address.

powerlevel9k.zsh-theme

@@ -1114,8 +1114,8 @@ prompt_swift_version() {
   "$1_prompt_segment" "$0" "$2" "magenta" "white" "${swift_version}" 'SWIFT_ICON'
 }
 
-# dir_permision: Display information about the user's permission to write in the current directory
-prompt_dir_permission() {
+# dir_writable: Display information about the user's permission to write in the current directory
+prompt_dir_writable() {
   if [[ ! -w "$PWD" ]]; then
     "$1_prompt_segment" "$0_FORBIDDEN" "$2" "red" "226" "" 'LOCK_ICON'
   fi