doc: mention coc explorer

related: #2235

doc/airline.txt

@@ -220,7 +220,9 @@ values):
   (for section a and b): >
 
   let g:airline_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', '' ],
       \ 'help':  [ 'Help', '%f' ],
       \ 'minibufexpl': [ 'MiniBufExplorer', '' ],
@@ -229,6 +231,7 @@ values):
       \ 'vim-plug': [ 'Plugins', '' ],
       \ 'vimfiler': [ 'vimfiler', '%{vimfiler#get_status_string()}' ],
       \ 'vimshell': ['vimshell','%{vimshell#get_status_string()}'],
+      \ 'vaffle' : [ 'Vaffle', '%{b:vaffle.dir}' ],
       \ }
 <
 * defines whether the preview window should be excluded from have its window