Minor 1.5 (#18)

- Updated repository documentation: added contribution guidelines, Code of Conduct, GitHub templates
- Updated README
- Added confirmation dialog for tabs and collections deletion (#17)
- Complete code refactoring (HTML/JS/CSS)
- Implemented <iframe> base for embedded pane (#13) (Fixed CSS instability on some websites)
- Improved dark theme
- Added opensource fonts to replace Segoe UI on Unix systems (#11, #17)
- Fixed invisible vertical scrollbar
- Code polish and improvement

Co-authored-by: Amine A. <15179425+AmineI@users.noreply.github.com>
Co-Authored-By: Michael Gordeev <michael@xfox111.net>

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,33 @@
+---
+name: Bug report
+about: Create a report to help us improve the extension
+title: ''
+labels: bug
+assignees: ''
+
+---
+
+### Description
+A clear and concise description of what the bug is.
+
+### Reproduction steps
+Steps to reproduce the behavior:
+1. Go to '...'
+2. Click on '...'
+3. Scroll down to '...'
+4. See error
+
+### Expected behavior
+A clear and concise description of what you expected to happen.
+
+### Screenshots
+If applicable, add screenshots to help explain your problem.
+
+### Environment
+Please provide the following information:
+ - Operating System: [e.g. Windows 10 Pro 1909 (10.0.18363)]
+ - Browser: [e.g. Microsoft Edge 83.0.478.56]
+ - Extension version: [e.g. 1.5]
+
+### Additional context
+Add any other context about the problem here.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,20 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: enhancement
+assignees: ''
+
+---
+
+**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 '...'
+
+**Describe the solution you'd like**
+A clear and concise description of what you want to happen.
+
+**Describe alternatives you've considered**
+A clear and concise description of any alternative solutions or features you've considered.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.

.github/pull_request_template.md

@@ -0,0 +1,9 @@
+Implements following issues: 
+
+## Changelog
+- Item 1
+- Item 2
+- Item 3
+
+## PR Checklist
+- [ ] Change extension version in the manifest