add lspsaga plugin and doc for it

README.md

@@ -321,6 +321,42 @@ GitSings provides some commands for displaying git stuff:
 |\<leader\>wr 	|remove workspace folder|
 |\<leader\>wl |	list workspace folders |
 
+#### Lspsaga plugin
+
+Display element (function or whatever?) hierarchy
+```bash
+:Lspsaga incoming_calls and :Lspsaga outgoing_calls
+```
+Show avaliable code actions for current line
+```bash
+:Lspsaga code_action
+```
+Element definition
+```text
+Invoke by running :Lspsaga peek_definition and :Lspsaga peek_type_definition. Layout is drawer and is currently the only one available. If you want to go to the definition, use :Lspsaga goto_definition and :Lspsaga goto_type_definition
+```
+Finder - find current element over all files
+```bash
+:Lspsaga finder
+```
+Floating terminal
+```bash
+:Lspsaga term_toggle
+```
+Show hover doc (Use `:Lspsaga hover_doc ++keep` if you want to keep the hover window.)
+```bash
+:Lspsaga hover_doc
+```
+Outline
+```bash
+:Lspsaga outline
+```
+Rename
+```bash
+:Lspsaga rename
+```
+
+
 #### LSP diagnostics (custom and trouble.nvim)
 
 |||