feat(repl): Add import-vcard and make-vcard commands (#7048)

- Added import-vcard and make-vcard commands to deltachat-repl. These
  wrap the corresponding import_vcard() and make_vcard() operations from
  src/contact.rs. Each command takes a file path argument specifying the
  location of the vCard file to be read or written. The make-vcard command
  takes one or more IDs to write to the file.
- Documented commands in "Using the CLI client" section of README.md.

Co-authored-by: iequidoo <117991069+iequidoo@users.noreply.github.com>

README.md

@@ -80,18 +80,26 @@ Connect to your mail server (if already configured):
 > connect
 ```
 
-Create a contact:
+Export your public key to a vCard file:
+
+```
+> make-vcard my.vcard 1
+```
+
+Create contacts by address or vCard file:
 
 ```
 > addcontact yourfriends@email.org
+> import-vcard key-contact.vcard
 ```
 
 List contacts:
 
 ```
 > listcontacts
+Contact#Contact#11: key-contact@email.org <key-contact@email.org>
 Contact#Contact#Self: Me √ <your@email.org>
-1 key contacts.
+2 key contacts.
 Contact#Contact#10: yourfriends@email.org <yourfriends@email.org>
 1 address contacts.
 ```