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

---------

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

lua/typstar/autosnippets.lua

@@ -32,6 +32,16 @@ function M.cap(i)
     return luasnip.function_node(function(_, snip) return snip.captures[i] end)
 end
 
+function M.leading_white_spaces(i)
+    -- isolate whitespaces of captured group
+    return luasnip.function_node(function(_, snip)
+        local capture = snip.captures[i] or '' -- Return capture or empty string if nil
+        -- Extract only leading whitespace using pattern matching
+        local whitespace = capture:match('^%s*') or ''
+        return whitespace
+    end)
+end
+
 function M.visual(idx, default)
     default = default or ''
     return luasnip.dynamic_node(idx, function(args, parent)
@@ -70,6 +80,17 @@ function M.start_snip(trigger, expand, insert, condition, priority)
     return M.snip('^(\\s*)' .. trigger, '<>' .. expand, { M.cap(1), unpack(insert) }, condition, priority)
 end
 
+function M.start_snip_in_newl(trigger, expand, insert, condition, priority)
+    return M.snip(
+        '([^\\s]\\s+)' .. trigger,
+        '<>\n<>' .. expand,
+        { M.cap(1), M.leading_white_spaces(1), unpack(insert) },
+        condition,
+        priority,
+        false
+    )
+end
+
 local alts_regex = '[\\[\\(](.*|.*)[\\)\\]]'
 
 function M.engine(trigger, opts)