added codecov

Author: jrzkaminski

.codecov.yml

@@ -5,4 +5,4 @@ coverage:
         threshold: 1%
     patch: false
 ignore:
-  - "fedot/external"  # external cannot be fully tested
+  - "bamt/external"  # external cannot be fully tested

README.rst

@@ -8,6 +8,8 @@
 
    * - package
      - | |pypi| |py_8| |py_9| |py_10|
+   * - tests
+     - | |coverage|
    * - docs
      - |docs|
    * - license
@@ -259,3 +261,6 @@ publisher={Elsevier}
 
 .. |downloads_weekly| image:: https://static.pepy.tech/personalized-badge/bamt?period=week&units=international_system&left_color=grey&right_color=blue&left_text=downloads/week
  :target: https://pepy.tech/project/bamt
+
+..|coverage| .. image:: https://codecov.io/gh/jrzkaminski/BAMT/branch/master/graph/badge.svg?token=DWDKGJ1RET 
+ :target: https://codecov.io/gh/jrzkaminski/BAMT