Fix first line in doc for local-additions

The documentation for vim help pages states that a first line is required
for the file to appear under `:help local-additions`, with the following
format: `*tag* description`

This change implements that

Author: jpc-hpe

doc/dap-python.txt

@@ -1,5 +1,5 @@
+*dap-python*                                     Python extension for nvim-dap
 ==============================================================================
-Python extension for nvim-dap                                       *dap-python*
 
 M.test_runner                                           *dap-python.test_runner*
      Test runner to use by default.