docs: Add jumplist documentation to the book

My spin on adding documentation for the jumplist to the book. Would love
to have other eyes on this and suggest ways to improve it.

Closes: #13594

book/src/SUMMARY.md

@@ -11,6 +11,7 @@
   - [Textobjects](./textobjects.md)
   - [Syntax aware motions](./syntax-aware-motions.md)
   - [Pickers](./pickers.md)
+  - [Jumplist](./jumplist.md)
   - [Keymap](./keymap.md)
   - [Command line](./command-line.md)
   - [Commands](./commands.md)

book/src/jumplist.md

@@ -0,0 +1,36 @@
+## Using the jumplist
+
+To help with quick navigation, Helix maintains a list of "jumps" called the jumplist.
+Whenever you make a significant movement (see next section), Helix stores your selections from before the move as a jump.
+A jump serves as a kind of checkpoint, allowing you to jump to a separate location, make edits, and return to where you were with your previous selections.
+This way, the jumplist tracks both your previous location and your selections.
+You can manually save a jump by using `Ctrl-s`.
+To jump backward in the jumplist, use `Ctrl-o`; to go forward, use `Ctrl-i`. To view and select from the full jumplist, use `Space-j` to open the jumplist picker.
+
+### What makes a jump
+The following is a non-exhaustive list of which actions add a jump to the jumplist:
+- Switching buffers
+  - Using the buffer picker, going to the next/previous buffer
+  - Going to the last accessed/modified file
+  - Making a new file (`:new FILE`)
+  - Opening a file (`:open FILE`)
+    - Includes `:log-open`, `:config-open`, `:config-open-workspace`, `:tutor`
+  - Navigating by pickers, global search, or the file explorer
+  - `goto_file` (`gf`)
+- Big in-file movements
+  - `select_regex` (`s`)
+  - `split_regex` (`S`)
+  - `search` (`/`)
+  - `keep_selections` and `remove_selections` (`K` and `<A-K>`)
+  - `goto_file_start` (`gg`)
+  - `goto_file_end`
+  - `goto_last_line` (`ge`)
+  - `:goto 123` / `:123` / `123G`
+  - `goto_definition` (`gd`)
+  - `goto_declaration` (`gD`)
+  - `goto_type_definition` (`gy`)
+  - `goto_reference` (`gr`)
+- Other
+  - `Ctrl-s` manually creates a jump
+  - Trying to close a modified buffer can switch you to that buffer and create a jump
+  - The debugger can create jumps as you jump stack frames