[Improvement] Add lspkind.nvim is a dependency, since it obviously is one.

Add lspkind.nvim as a dependency.

Without it, I get the error:

Error executing Lua callback: ...issues-minimal/lazy/lspsaga.nvim/lua/lspsaga/lspkind.lua:1: attempt to index field 'config' (a nil value)                  
stack traceback:                                                                                                                                            
        ...issues-minimal/lazy/lspsaga.nvim/lua/lspsaga/lspkind.lua:1: in main chunk                                                                        
        [C]: in function 'require'                                                                                                                          
        ...minimal/lazy/lspsaga.nvim/lua/lspsaga/symbol/outline.lua:5: in main chunk                                                                        
        [C]: in function 'require'                                                                                                                          
        ...es-minimal/lazy/lspsaga.nvim/lua/lspsaga/symbol/init.lua:222: in function 'outline'                                                              
        ...issues-minimal/lazy/lspsaga.nvim/lua/lspsaga/command.lua:50: in function <...issues-minimal/lazy/lspsaga.nvim/lua/lspsaga/command.lua:49>        
        ...issues-minimal/lazy/lspsaga.nvim/lua/lspsaga/command.lua:80: in function 'load_command'                                                          
        ...nvim-issues-minimal/lazy/lspsaga.nvim/plugin/lspsaga.lua:8: in function <...nvim-issues-minimal/lazy/lspsaga.nvim/plugin/lspsaga.lua:7> 

Start from lua/lspsaga/lspkind.lua and the dependency configuration used by the plugin. Reproduce the outline command that triggers the reported nil config error, then verify that lspkind.nvim is installed and the error no longer occurs.