chore: update readme for older vim versions

Author: dlvandenberg

README.md

@@ -32,6 +32,8 @@ This parser extends [tree-sitter-html](https://github.com/tree-sitter/tree-sitte
 
 In the nightly neovim built (or release 0.11.x), the filetype detection for Angular templates is included. It will detect Angular HTML templates, based on it's contents, and set the filetype to `htmlangular`.
 
+### Older versions
+
 If you are using an older version, you must set the filetype yourself.
 
 E.g. mark the file as `htmlangular` if it matches the pattern `*.component.html`:
@@ -46,6 +48,18 @@ vim.filetype.add({
 })
 ```
 
+Next, create a `ftplugin` for `htmlangular` that does the following:
+
+```vim
+runtime! ftplugin/html.vim!
+```
+
+Or, in lua:
+
+```lua
+vim.cmd('runtime! ftplugin/html.vim!')
+```
+
 ## LSP's or other plugins
 
 You may need to include this new filetype (`htmlangular`) for other plugins, like [LSP](https://github.com/neovim/nvim-lspconfig/blob/master/doc/server_configurations.md#angularls) for example: