ADD 12.0 module company_code (#77)

* ADD module company_code

* FIX doc

* FIX doc

* Update company_code/readme/USAGE.rst

Co-Authored-By: bealdav <david.beal@akretion.com>

company_code/readme/CONTRIBUTORS.rst

@@ -0,0 +1 @@
+David Beal <david.beal@akretion.com>

company_code/readme/DESCRIPTION.rst

@@ -0,0 +1,2 @@
+- add `code` field to company.
+- update name_get with this field

company_code/readme/USAGE.rst

@@ -0,0 +1,11 @@
+To display your company code with `name_get()` just 
+write this in your custom code according to your model
+
+
+```python
+class ResPartner(models.Model):
+    _inherit = 'res.partner'
+
+    def name_get(self):
+        return self.env['res.company']._add_company_code(super())
+```