add support for tables without borders

i.e.
```
header 1|header 2
--|--
data 1|data 2
```

ftplugin/markdown.vim

@@ -538,6 +538,15 @@ endfunction
 "
 function! s:TableFormat()
     let l:pos = getpos('.')
+
+    normal! {
+    call search('|')
+    execute 'silent .,''}s/\v^(\s{0,})\|?([^\|])/\1|\2/e'
+
+    normal! {
+    call search('|')
+    execute 'silent .,''}s/\v([^\|])\|?(\s{0,})$/\1|\2/e'
+
     normal! {
     " Search instead of `normal! j` because of the table at beginning of file edge case.
     call search('|')
@@ -765,7 +774,7 @@ endif
 command! -buffer -range=% HeaderDecrease call s:HeaderDecrease(<line1>, <line2>)
 command! -buffer -range=% HeaderIncrease call s:HeaderDecrease(<line1>, <line2>, 1)
 command! -buffer -range=% SetexToAtx call s:SetexToAtx(<line1>, <line2>)
-command! -buffer TableFormat call s:TableFormat()
+command! -range TableFormat '<,'> call s:TableFormat()
 command! -buffer Toc call s:Toc()
 command! -buffer Toch call s:Toc('horizontal')
 command! -buffer Tocv call s:Toc('vertical')