feat: Add follow_cursor and restore_location

New lua API function: follow_cursor (supports opts.focus_outline).
This sets location in outline to match location in code.

New keymap: restore_location (C-g) by default.
This provides the same functionality as follow_cursor.

I've also refactored other lua API functions for consistency of using
`opts.focus_outline`. If opts is not provided, focus_outline is
defaulted to true. To change this behaviour, set it to false.

lua/symbols-outline/providers/nvim-lsp.lua

@@ -69,13 +69,14 @@ function M.postprocess_symbols(response)
 end
 
 ---@param on_symbols function
-function M.request_symbols(on_symbols)
+function M.request_symbols(on_symbols, opts)
   vim.lsp.buf_request_all(
     0,
     'textDocument/documentSymbol',
     getParams(),
     function (response)
-      on_symbols(M.postprocess_symbols(response))
+      response = M.postprocess_symbols(response)
+      on_symbols(response, opts)
     end
   )
 end