Expand 2026 interview prep guide with complete practices and required skillsets

[Copilot]

The repo only had a placeholder line for interview prep, which did not satisfy the request to display all practices and skillsets needed for 2026 tech interviews. This update turns the README into a structured, comprehensive prep guide.

• Scope

  • Replaced the minimal README content with a full 2026 interview-prep reference.
  • Kept changes isolated to README.md (no code/config/tooling changes).

• Interview Practices (execution-focused)

  • Added concrete practice patterns: timed coding reps, mock loop cadence, debugging drills, STAR story prep, system design rehearsal, and communication habits.

• Required Skillsets (organized by domain)

  • Added grouped skill expectations across:
    • Core coding (DSA + complexity)
    • Software engineering fundamentals (clean code, APIs, data, concurrency)
    • System design/platform (distributed systems, reliability, cloud, security)
    • AI-era readiness (AI-assisted development, LLM feature literacy, responsible AI)
    • Collaboration/communication (tradeoff articulation, product thinking, cross-functional execution)

• Example excerpt

  ## Practices for a 2026 Tech Interview
  - Build a 6-8 week study plan with weekly targets for algorithms, system design, and behavioral prep.
  - Practice coding interviews in timed sessions (35-45 minutes) and explain tradeoffs out loud.
  
  ## Skillset Needed for 2026 Interviews
  ### AI-Era Readiness (2026)
  - Evaluating AI-generated code for correctness, security, and maintainability.
  - Practical understanding of LLM-enabled features, embeddings, and retrieval patterns.

Original prompt

Display all the practices and skillset needed for tech interview in 2026