chore: fix typo in README (#1439)

Author: vegerot

README.markdown

@@ -87,7 +87,7 @@ After installing NERDTree, the best way to learn it is to turn on the Quick Help
 NERDTree can be extended with custom mappings and functions using its built-in API. The details of this API are described in the included documentation. Several plugins have been written, and are available on Github for installation like any other plugin. The plugins in this list are maintained (or not) by their respective owners, and certain combinations may be incompatible.
 
 * [Xuyuanp/nerdtree-git-plugin](https://github.com/Xuyuanp/nerdtree-git-plugin): Shows Git status flags for files and folders in NERDTree.
-* [ryanoasis/vim-devicons](https://github.com/ryanoasis/vim-devicons): Adds filetype-specific icons to NERDTree files and folders,
+* [ryanoasis/vim-devicons](https://github.com/ryanoasis/vim-devicons): Adds filetype-specific icons to NERDTree files and folders.
 * [tiagofumo/vim-nerdtree-syntax-highlight](https://github.com/tiagofumo/vim-nerdtree-syntax-highlight): Adds syntax highlighting to NERDTree based on filetype.
 * [scrooloose/nerdtree-project-plugin](https://github.com/scrooloose/nerdtree-project-plugin): Saves and restores the state of the NERDTree between sessions.
 * [PhilRunninger/nerdtree-buffer-ops](https://github.com/PhilRunninger/nerdtree-buffer-ops): 1) Highlights open files in a different color. 2) Closes a buffer directly from NERDTree.