Fix README grammar and improve phrasing

[penggrin12]

Description

Fixes grammar, phrasing, and consistency issues in README.md.

Changes

• Corrected verb agreement (e.g., "assumes" -> "assume", "have" -> "has").
• Replaced incorrect word forms (e.g., "sequentiality" -> "sequentially", "setup" -> "set up" when used as a verb).
• Fixed missing/extra words (e.g., "appid based" -> "appid-based search path is an issue").
• Standardized style (e.g., "Metamod" capitalization, "showup" -> "show up").
• Minor polish for clarity and readability.

[sunzenshen]

@penggrin12 You're good to go to merge, if you're ready.

[Rainyan]

Since this looks all good, I took the liberty to merge it in. Thanks for the PR!