Test all features

Add cases for attribute highlight on and off, block syntax by lang
and emmet-vim group names, OnChangeVueSyntax(), matchit, .wpy,
initial_indent as syntax and tag.syntax, and syntax after reloading.

Also check indenting a file after removing all indent with
g:test_flatten, which fails before the end tag fix as closing tags at
column 0 were taken as block end tags.

test/cases/basic.vim

@@ -5,3 +5,15 @@ let g:vim_vue_plugin_config = {
       \   'style': ['css'],
       \},
       \}
+let g:test_flatten = 1
+packadd matchit
+
+" Jump between tags with % by matchit. Use :normal for its mapping
+function! Check()
+  for [lnum, col, expected] in [[1, 2, [3, '/template']], [2, 4, [2, '/p']]]
+    call cursor(lnum, col)
+    normal %
+    call ExpectEqual([line('.'), matchstr(getline('.'), '\%'.col('.').'c/\w\+')],
+          \ expected, printf('after %% from line %d col %d', lnum, col))
+  endfor
+endfunction