feat: add vim.secure.read()

This function accepts a path to a file and prompts the user if the file
is trusted. If the user confirms that the file is trusted, the contents
of the file are returned. The user's decision is stored in a trust
database at $XDG_STATE_HOME/nvim/trust. When this function is invoked
with a path that is already marked as trusted in the trust database, the
user is not prompted for a response.

scripts/gen_vimdoc.py

@@ -131,6 +131,7 @@ CONFIG = {
             'filetype.lua',
             'keymap.lua',
             'fs.lua',
+            'secure.lua',
         ],
         'files': [
             'runtime/lua/vim/_editor.lua',
@@ -140,6 +141,7 @@ CONFIG = {
             'runtime/lua/vim/filetype.lua',
             'runtime/lua/vim/keymap.lua',
             'runtime/lua/vim/fs.lua',
+            'runtime/lua/vim/secure.lua',
         ],
         'file_patterns': '*.lua',
         'fn_name_prefix': '',
@@ -166,6 +168,7 @@ CONFIG = {
             'filetype': 'vim.filetype',
             'keymap': 'vim.keymap',
             'fs': 'vim.fs',
+            'secure': 'vim.secure',
         },
         'append_only': [
             'shared.lua',