feat(event): add WillCreateFile, WillRemoveFile (#2273)

node. These are mostly going to be useful for implementing lsp file
operation actions.

Co-authored-by: Alexander Courtis <alex@courtis.org>

doc/nvim-tree-lua.txt

@@ -2186,10 +2186,20 @@ e.g. handler for node renamed: >
                 handler parameters: ~
                   {fname}        `{string}` Absolute path to the created file
 
+- Event.WillCreateFile
+                handler parameters: ~
+                  {fname}        `{string}` Absolute path to the file to be
+                  created
+
 - Event.FileRemoved
                 handler parameters: ~
                   {fname}        `{string}` Absolute path to the removed file.
 
+- Event.WillRemoveFile
+                handler parameters: ~
+                  {fname}        `{string}` Absolute path to the file to be
+                  removed
+
 - Event.FolderCreated
                 handler parameters: ~
                   {folder_name}  `{string}` Absolute path to the created folder.