Implement new functions of NVIM API v6

[esensar]

Implement new functions added in NVIM API v6. These functions can be discovered using API Explorer from this project. All of this belongs to neovim-api module and wrappers need to be made in neovim-rx-api module for RxJava support.

These are:

• Functions:
  • nvim_ui_try_resize_grid - https://neovim.io/doc/user/api.html#nvim_ui_try_resize_grid()
  • nvim_ui_pum_set_height - https://neovim.io/doc/user/api.html#nvim_ui_pum_set_height()
  • nvim_input_mouse - https://neovim.io/doc/user/api.html#nvim_input_mouse()
  • nvim_set_vvar - https://neovim.io/doc/user/api.html#nvim_set_vvar()
  • nvim_create_buf - https://neovim.io/doc/user/api.html#nvim_create_buf()
  • nvim_open_win - https://neovim.io/doc/user/api.html#nvim_open_win()
  • nvim_paste - https://neovim.io/doc/user/api.html#nvim_paste()
  • nvim_put - https://neovim.io/doc/user/api.html#nvim_put()
  • nvim_get_context - https://neovim.io/doc/user/api.html#nvim_get_context()
  • nvim_load_context - https://neovim.io/doc/user/api.html#nvim_load_context()
  • nvim_set_keymap - https://neovim.io/doc/user/api.html#nvim_set_keymap()
  • nvim_del_keymap - https://neovim.io/doc/user/api.html#nvim_del_keymap()
  • nvim_select_popupmenu_item - https://neovim.io/doc/user/api.html#nvim_select_popupmenu_item()
• Methods:
  • nvim_buf_set_keymap - https://neovim.io/doc/user/api.html#nvim_buf_set_keymap()
  • nvim_buf_del_keymap - https://neovim.io/doc/user/api.html#nvim_buf_del_keymap()
  • nvim_win_set_config - https://neovim.io/doc/user/api.html#nvim_win_set_config()
  • nvim_win_get_config - https://neovim.io/doc/user/api.html#nvim_win_get_config()
  • nvim_win_close - https://neovim.io/doc/user/api.html#nvim_win_close()