feat(snip): expand into next line with correct indent (#13)

* New snippet type. Expand from nonempty line into next line.

* Fix trigger to ' dm' instead of 'dm'

* style: format code

* minor: improve regex

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Co-authored-by: arne314 <73391160+arne314@users.noreply.github.com>

lua/typstar/snippets/markup.lua

@@ -43,6 +43,12 @@ end
 
 return {
     start('dm', '$\n<>\t<>\n<>$', { cap(1), visual(1), cap(1) }, markup),
+    helper.start_snip_in_newl(
+        'dm',
+        '$\n<>\t<>\n<>$',
+        { helper.leading_white_spaces(1), visual(1), helper.leading_white_spaces(1) },
+        markup
+    ),
     start('fla', '#flashcard(0)[<>][\n<>\t<>\n<>]', { i(1, 'flashcard'), cap(1), visual(2), cap(1) }, markup),
     start('flA', '#flashcard(0, "<>")[\n<>\t<>\n<>]', { i(1, 'flashcard'), cap(1), visual(2), cap(1) }, markup),
     snip('IMP', '$==>>$ ', {}, markup),