Add keymap extension which shows keymap setting.

autoload/airline/extensions/keymap.vim

@@ -0,0 +1,20 @@
+" MIT License. Copyright (c) 2017 Doron Behar.
+
+scriptencoding utf-8
+
+if !has('keymap')
+	finish
+endif
+
+function! airline#extensions#keymap#status()
+	if &keymap != ''
+		let s:keymap2print = g:airline_symbols.keymap . ' ' . &keymap
+	else
+		let s:keymap2print = ''
+	endif
+	return printf('%s', s:keymap2print)
+endfunction
+
+function! airline#extensions#keymap#init(ext)
+  call airline#parts#define_function('keymap', 'airline#extensions#keymap#status')
+endfunction

doc/airline.txt

@@ -866,6 +866,12 @@ vim-xkblayout
   macOS (Install https://github.com/vovkasm/input-source-switcher):
    let g:XkbSwitchLib = '/usr/local/lib/libInputSourceSwitcher.dylib'
 
+-------------------------------------                     *airline-keymap*
+vim-keymap
+
+* enable/disable vim-keymap extension >
+  let g:airline#extensions#keymap#enabled = 1
+
 -------------------------------------                   *airline-windowswap*
 vim-windowswap <https://github.com/wesQ3/vim-windowswap>