issue templates: add generic option & more links

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,11 @@
+blank_issues_enabled: false
+contact_links:
+- name: Announcement
+  url: https://www.ccpsynerbi.ac.uk/events/petric/
+  about: CCP SyneRBI website Challenge announcement
+- name: Wiki
+  url: https://github.com/SyneRBI/PETRIC/wiki
+  about: Participation details
+- name: Leaderboard
+  url: https://tomography.stfc.ac.uk
+  about: Current rankings

.github/ISSUE_TEMPLATE/issue.md

@@ -0,0 +1,4 @@
+---
+name: Bug or Enhancement
+about: unexpected behaviour, feature request, or documentation suggestion
+---

README.md

@@ -1,10 +1,10 @@
 # PETRIC: PET Rapid Image reconstruction Challenge
 
-[![website](https://img.shields.io/badge/website-announcement-green)](https://www.ccpsynerbi.ac.uk/events/petric/) [![wiki](https://img.shields.io/badge/details-wiki-blue)](https://github.com/SyneRBI/PETRIC/wiki) [![Leaderboard](https://img.shields.io/badge/leaderboard-orange)](https://tomography.stfc.ac.uk)
+[![website](https://img.shields.io/badge/website-announcement-purple)](https://www.ccpsynerbi.ac.uk/events/petric/) [![wiki](https://img.shields.io/badge/details-wiki-blue)](https://github.com/SyneRBI/PETRIC/wiki) [![registration](https://img.shields.io/badge/participate-registration-green)](https://github.com/SyneRBI/PETRIC/issues/new/choose) [![leaderboard](https://img.shields.io/badge/leaderboard-orange)](https://tomography.stfc.ac.uk)
 
 ## Participating
 
-The organisers will provide GPU-enabled cloud runners which have access to larger private datasets for evaluation. To gain access, you must [register by opening an issue](https://github.com/SyneRBI/PETRIC/issues/new/choose). The organisers will then create a private team submission repository for you.
+The organisers will provide GPU-enabled cloud runners which have access to larger private datasets for evaluation. To gain access, you must [register](https://github.com/SyneRBI/PETRIC/issues/new/choose). The organisers will then create a private team submission repository for you.
 
 ## Layout