minor #371 [Maintenance] Update README and PR template (GSadee)

This PR was merged into the 1.0 branch.

Discussion
----------

| Q               | A
| --------------- | -----
| Branch?         | 1.0
| Bug fix?        | yes
| New feature?    | no
| Related tickets | 


Commits
-------

f82c523 [Maintenance] Update README and PR template

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,6 +1,6 @@
 | Q               | A
 | --------------- | -----
-| Branch?         | 1.0 (security fixes), 1.1 (bug fixes, improvements), master (new features)
+| Branch?         | 1.1 (security fixes), 1.2 (bug fixes, improvements), 1.3 (new features)
 | Bug fix?        | no/yes
 | New feature?    | no/yes
 | Related tickets | fixes #X, partially #Y, mentioned in #Z

README.md

@@ -125,9 +125,9 @@ Tagged services would be executed according to their priority (descending).
 
 ## Supported branches
 
-* `1.0` (v1.0.*) - security fixes
-* `1.1` (v1.1.*) - bug fixes, improvements
-* `1.2` (v1.2.*) - new features
+* `1.1` (v1.1.*) - security fixes
+* `1.2` (v1.2.*) - bug fixes, improvements
+* `1.3` (v1.3.*) - new features
 * `2.0` (v2.0.*) - new features, removing deprecations, potential BC breaks
 
 ## Security issues