feat(babel): add shebang support for tangled code blocks

Add the ability to include a shebang line at the beginning of tangled code files
by supporting the `:shebang` header argument. The shebang value is cleaned of
quotes and inserted as the first line of the tangled content.

lua/orgmode/babel/tangle.lua

@@ -60,6 +60,13 @@ function Tangle:tangle()
       vim.fn.mkdir(path, 'p')
     end
 
+    local shebang = info.header_args[':shebang']
+    if shebang then
+      shebang = shebang:gsub('[\'"]', '')
+      utils.echo_info(('shebang: %s'):format(shebang))
+      table.insert(parsed_content, 1, shebang)
+    end
+
     if info.name then
       block_content_by_name[info.name] = parsed_content
     end