Allow additional override fields such as priority filter

[ranebrown]

Using g:lsp_settings doesn't seem to allow adding extra override fields that are not predefined. For example, using asyncomplete and the option g:asyncomplete_preprocessor to define a priority as outlined in the documentation would require adding a field 'priority': 50 but this gets ignored. Is there a way around this or can the ability to add additional fields be added?

[mattn]

@prabirshrestha any thought?

[ranebrown]

Any ideas on this? Would a PR be accepted?

[mattn]

vim-lsp provide completion but not depend on asyncomplete directly. So it need to add namespace for structure. i think.