Update issue templates

.github/ISSUE_TEMPLATE/add-short-link.md

@@ -0,0 +1,14 @@
+---
+name: Add short-link
+about: Propose a short-link
+title: ''
+labels: new short-link
+assignees: ''
+
+---
+
+<!--
+list all of your proposed short-links in the format
+* /short-link https://tu-ilmenau.de/target
+and state why
+-->

.github/ISSUE_TEMPLATE/custom.md

@@ -0,0 +1,10 @@
+---
+name: Custom issue template
+about: Describe this issue template's purpose here.
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+