feat: add border config for SSH and keymaps help window (#299)

* feat: add config for ssh window border

* chore: add documentation for ssh window border

* feat: add config for keymaps help window border

* chore: add documentatoin for keymaps help window border

lua/oil/adapters/ssh/connection.lua

@@ -1,3 +1,4 @@
+local config = require("oil.config")
 local layout = require("oil.layout")
 local util = require("oil.util")
 
@@ -277,7 +278,7 @@ function SSHConnection:open_terminal()
     row = row,
     col = col,
     style = "minimal",
-    border = "rounded",
+    border = config.ssh.border,
   })
   vim.cmd.startinsert()
 end