Update isort.cfg and .pre-commit-config.yaml

Adds 'add trailing commas' hook and changes isort to not re-write each other

.isort.cfg

@@ -14,3 +14,5 @@ known_third_party =
     taxii2client,
 known_first_party = stix2
 force_sort_within_sections = 1
+multi_line_output = 5
+include_trailing_comma = True

.pre-commit-config.yaml

@@ -1,11 +1,16 @@
+repos:
 -   repo: https://github.com/pre-commit/pre-commit-hooks
-    sha: v0.9.4
+    rev: v1.3.0
     hooks:
     -   id: trailing-whitespace
     -   id: flake8
         args:
         - --max-line-length=160
     -   id: check-merge-conflict
+-   repo: https://github.com/asottile/add-trailing-comma
+    rev: v0.6.4
+    hooks:
+    -   id: add-trailing-comma
 -   repo: https://github.com/FalconSocial/pre-commit-python-sorter
     sha: b57843b0b874df1d16eb0bef00b868792cb245c2
     hooks: