Change format of GitHub issue templates

Author: olivervogel

.github/ISSUE_TEMPLATE/bug_report.md

@@ -7,19 +7,19 @@ assignees: ''
 
 ---
 
-**Describe the bug**
+## Describe the bug
 A clear and concise description of what the bug is.
 
-**Code Example**
+## Code Example
 Code example to reproduce the behavior.
 
-**Expected behavior**
+## Expected behavior
 A clear and concise description of what you expected to happen.
 
-**Images**
+## Images
 If applicable, add problematic images or screenshots to help explain your problem.
 
-**Environment (please complete the following information):**
+## Environment (please complete the following information):
  - PHP Version:
  - OS:
  - Intervention Image Version:

.github/ISSUE_TEMPLATE/feature_request.md

@@ -7,8 +7,8 @@ assignees: ''
 
 ---
 
-**Describe the feature you'd like**
+## Describe the feature you'd like
 A clear and concise description of what you want to happen.
 
-**Is your feature request related to a problem? Please describe.**
+## Is your feature request related to a problem? Please describe.
 A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]