fix(markdown): Ensure content is followed by '#'

Before this commit, empty headings are taken into account:

   # a normal heading

   below is not a good heading:

   #

   below is also not a good heading:

   ##

   These should not be listed in the outline.

README.md

@@ -47,6 +47,8 @@ I do not merge PRs from the original repo that I don't personally need.
 - Open handler triggering multiple times ends up in messy state with errors
   simrat39/symbols-outline.nvim#235
 - Fixed `_highlight_current_item` function checking provider on outline window
+- Fixed behaviour of empty markdown headings `^(#+)(%s+)$` being listed in the
+outline.
 
 ## 🛑 Breaking changes
 

lua/symbols-outline/markdown.lua

@@ -15,11 +15,14 @@ function M.handle_markdown()
     if string.find(value, '^```') then
       is_inside_code_block = not is_inside_code_block
     end
+    if is_inside_code_block then
+      goto nextline
+    end
 
     local next_value = lines[line+1]
     local is_emtpy_line = #value:gsub("^%s*(.-)%s*$", "%1") == 0
 
-    local header, title = string.match(value, '^(#+)%s+(.*)$')
+    local header, title = string.match(value, '^(#+)%s+(.+)$')
     if not header and next_value and not is_emtpy_line then
       if string.match(next_value, '^=+%s*$') then
         header = '#'
@@ -29,8 +32,14 @@ function M.handle_markdown()
         title = value
       end
     end
+    if not header or not title then
+      goto nextline
+    end
+    -- TODO: This is not needed and it works?
+    -- if #header > 6 then
+    --   goto nextline
+    -- end
 
-    if header and not is_inside_code_block then
     local depth = #header + 1
 
     local parent
@@ -66,7 +75,7 @@ function M.handle_markdown()
 
     parent[#parent + 1] = entry
     level_symbols[depth] = entry
-    end
+    ::nextline::
   end
 
   for i = 2, max_level do