Fix/minor tweaks

[asboyer]

This pull request introduces several improvements focused on enhancing the blog's description, mobile responsiveness, and overall visual polish. The most significant changes include updating the blog description, improving mobile styles for both content and navigation, and refining the appearance of the blog description and tag/category lists.

Content and Description Updates:

• Updated the blog_description in _config.yml to a more descriptive and welcoming message, aiming to better communicate the blog's purpose.
• Added the blog description to the blog header in _pages/blog.md, displaying it only when present.
• Styled the .blog-description class in _sass/_base.scss for improved appearance and ensured it is hidden on screens smaller than 768px for better mobile experience.

Mobile and Responsive Design Improvements:

• Improved font sizes and line heights for #markdown-content and .post-title on smaller screens in both _sass/_base.scss and directly in the post markdown for better readability on mobile devices. [1] [2] [3]
• Enhanced the layout of the featured posts row in _pages/blog.md to use a single column on extra-small screens for better mobile support.
• Refined padding and display of tag/category lists and navigation elements for smaller screens to improve usability and appearance. [1] [2]

Visual and Usability Enhancements:

• Hid the browser scrollbar while maintaining scroll functionality for a cleaner look in _sass/_base.scss.
• Minor HTML formatting improvements in the Substack link in _includes/social.liquid for consistency.