feat: clear lsp references on ui open

if you are hovering over some text with an lsp, it highlights
all the references, when entering ssr these highlights are still
visible, this can be visually noisy

lua/ssr.lua

@@ -78,6 +78,13 @@ function Ui:open()
   self.ns = api.nvim_create_namespace ""
   self.cur_match_ns = api.nvim_create_namespace ""
 
+  local function clear_extmark(namespace)
+    local ns_id = vim.api.nvim_get_namespaces()[namespace]
+    vim.api.nvim_buf_clear_namespace(self.origin_buf, ns_id, 0, -1)
+  end
+
+  pcall(clear_extmark, "vim_lsp_references")
+
   local function set_extmark(row, text)
     return api.nvim_buf_set_extmark(self.ui_buf, self.ns, row, 0, { virt_text = text, virt_text_pos = "overlay" })
   end