Support coc-explorer (file explorer extension)

autoload/airline/extensions.vim

@@ -23,6 +23,7 @@ endfunction
 let s:script_path = tolower(resolve(expand('<sfile>:p:h')))
 
 let s:filetype_overrides = {
+      \ 'coc-explorer':  [ 'CoC Explorer', '' ],
       \ 'defx':  ['defx', '%{b:defx.paths[0]}'],
       \ 'fugitive': ['fugitive', '%{airline#util#wrap(airline#extensions#branch#get_head(),80)}'],
       \ 'gundo': [ 'Gundo', '' ],