Add SEO-Linking-Guide.md: Beginner-friendly SEO and digital marketing guide

[Copilot]

This PR adds a comprehensive SEO & Digital Marketing Guide as SEO-Linking-Guide.md to provide users with simple, anxiety-free advice on website linking for SEO purposes.

What's Added

The new guide provides:

• Beginner-friendly explanations of SEO and website linking without technical jargon
• Practical strategies that require no coding or technical background
• Step-by-step weekly action plans for getting started with SEO
• Clear guidance on what to do and what to avoid when building links
• Mental health-conscious approach emphasizing "progress over perfection"

Key Features

• 📚 151 lines of well-structured content with 29 clear headings
• 🧠 Anxiety-free approach aligned with the repository's mental health support mission
• 👥 Accessible language designed for users without technical expertise
• 🛠️ Actionable advice including free tools and measurement strategies
• ✅ Safe practices with clear warnings about what to avoid

Content Highlights

The guide covers essential topics including:

• Understanding SEO basics in simple terms
• Internal and external linking strategies
• Building genuine relationships for natural link building
• Guest writing opportunities
• Free tools for beginners
• Measuring success without getting overwhelmed

This addition enhances the tweaks repository by providing valuable digital marketing resources that support users in improving their online presence while maintaining the project's commitment to accessibility and mental health awareness.

This pull request was created as a result of the following prompt from Copilot chat.

Add the SEO & Digital Marketing Guide (from 'b_spicy_firebase_fintech_starter_kit (2).js') to the tweaks repo as a new, easy-to-read Markdown file, so users can quickly access simple, anxiety-free advice on linking websites for SEO. The new file should be named 'SEO-Linking-Guide.md' and contain the full content of the provided guide, formatted for clarity and simplicity. No technical background should be required to use or understand this file.

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