jump: add README (#7237)

plugins/jump/README.md

+# Jump plugin
+
+This plugin allows to easily jump around the file system by manually adding marks.
+Those marks are stored as symbolic links in the directory `$MARKPATH` (default `$HOME/.marks`)
+
+To use it, add `jump` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... jump)
+```
+
+## Commands
+
+| Command              | Description                                                                                     |
+|----------------------|-------------------------------------------------------------------------------------------------|
+| `jump <mark-name>`   | Jump to the given mark                                                                          |
+| `mark [mark-name]`   | Create a mark with the given name or with the name of the current directory if none is provided |
+| `unmark <mark-name>` | Remove the given mark                                                                           |
+| `marks`              | List the existing marks and the directories they point to                                       |