Add documentation about information leaks in Vim/Neovim (#1674)

* Add documentation about using Vim/Neovim as editor
* Add documentation about information leaks in editors
* Spelling fix

---------

Co-authored-by: Jonathan Wren <jonathan@nowandwren.com>

docs/privacy-and-security.md

@@ -67,6 +67,84 @@ Windows doesn't log history to disk, but it does keep it in your command prompt
 session. Close the command prompt or press `Alt`+`F7` to clear your history
 after journaling.
 
+## Editor history
+
+Some editors keep usage history stored on disk for future use. This can be a
+security risk in the sense that sensitive information can leak via recent
+search patterns or editor commands.
+
+### Vim
+
+Vim stores progress data in a so called Viminfo file located at `~/.viminfo`
+which contains all sorts of user data including command line history, search
+string history, search/substitute patterns, contents of register etc. Also to
+be able to recover opened files after an unexpected application close Vim uses
+swap files.
+
+These options as well as other leaky features can be disabled by setting the
+`editor` key in the Jrnl settings like this:
+
+``` yaml
+editor: "vim -c 'set viminfo= noswapfile noundofile nobackup nowritebackup noshelltemp history=0 nomodeline secure'"
+```
+
+To disable all plugins and custom configurations and start Vim with the default
+configuration `-u NONE` can be passed on the command line as well. This will
+ensure that any rogue plugins or other difficult to catch information leaks are
+eliminated. The downside to this is that the editor experience will decrease
+quite a bit.
+
+To instead let Vim automatically detect when a Jrnl file is being edited an
+autocommand can be used. Place this in your `~/.vimrc`:
+
+``` vim
+autocmd BufNewFile,BufReadPre *.jrnl setlocal viminfo= noswapfile noundofile nobackup nowritebackup noshelltemp history=0 nomodeline secure
+```
+
+Please see `:h <option>` in Vim for more information about the options mentioned.
+
+### Neovim
+
+Neovim strives to be mostly compatible with Vim and has therefore similar
+functionality as Vim. One difference in Neovim is that the Viminfo file is
+instead called the ShaDa ("shared data") file which resides in
+`~/.local/state/nvim` (`~/.local/share/nvim` pre Neovim v0.8.0). The ShaDa file
+can be disabled in the same way as for Vim.
+
+``` yaml
+editor: "nvim -c 'set shada= noswapfile noundofile nobackup nowritebackup noshelltemp history=0 nomodeline secure'"
+```
+
+`-u NONE` can be passed here as well to start a session with the default configs.
+
+As for Vim above we can create an autocommand in Vimscript:
+
+``` vim
+autocmd BufNewFile,BufReadPre *.jrnl setlocal shada= noswapfile noundofile nobackup nowritebackup noshelltemp history=0 nomodeline secure
+```
+
+or the same but in Lua:
+
+``` lua
+vim.api.nvim_create_autocmd( {"BufNewFile","BufReadPre" }, {
+  group = vim.api.nvim_create_augroup("PrivateJrnl", {}),
+  pattern = "*.jrnl",
+  callback = function()
+    vim.o.shada = ""
+    vim.o.swapfile = false
+    vim.o.undofile = false
+    vim.o.backup = false
+    vim.o.writebackup = false
+    vim.o.shelltemp = false
+    vim.o.history = 0
+    vim.o.modeline = false
+    vim.o.secure = true
+  end,
+})
+```
+
+Please see `:h <option>` in Neovim for more information about the options mentioned.
+
 ## Files in transit from editor to jrnl
 
 When creating or editing an entry, `jrnl` uses a unencrypted temporary file on