Implement stick_to_left in center-alignment mode

autoload/easy_align.vim

@@ -414,6 +414,15 @@ function! s:do_align(modes, all_tokens, all_delims, fl, ll, fc, lc, pattern, nth
       let strip = float2nr(ceil((max.token_len - max.strip_len) / 2.0))
       let token = repeat(' ', float2nr(pf1)) .token. repeat(' ', float2nr(p2))
       let token = substitute(token, repeat(' ', strip) . '$', '', '')
+
+      if a:stick_to_left
+        if empty(s:rtrim(token))
+          let center = len(token) / 2
+          let [token, rpad] = [strpart(token, 0, center), strpart(token, center)]
+        else
+          let [token, rpad] = [s:rtrim(token), matchstr(token, '\s*$')]
+        endif
+      endif
     endif
     let tokens[nth] = token
 

test/basic.expected

@@ -1041,3 +1041,10 @@ aaaaaaaaaaa  = 123
 
 ```
 
+ a,    ,   bbb
+ aa,   ,   bb
+aaa,   ,    b
+aaaa,  ,
+aaa,   b,
+ aa,  bb,
+ a,   bbb,

test/basic.md

@@ -258,3 +258,10 @@ cccccccccccccccccc = 12345678 =
 
 ```
 
+a,,bbb
+aa,,bb
+aaa,,b
+aaaa,,
+aaa,b,
+aa,bb,
+a,bbb,

test/basic.script

@@ -1 +1 @@
-4Gvipjyvip
+4Gvipjyvip