Fix README.md typos, grammar, and structural inconsistencies

[Copilot]

README.md contained several typos, grammar errors, and structural inconsistencies that reduced clarity and professionalism.

Corrections

• HTML: secset → srcset in <source> tag
• Grammar/wording:
  • "QSOsin" → "QSOs in" (missing space)
  • "is not support" → "does not support"
  • "is available" → "are available" (subject-verb agreement)
  • Removed misplaced "Unfortunately" from uninstall instructions
  • "prioritised on Github" → "prioritized on GitHub"
• Code example: print(df) → print(df_adi) (wrong variable name)
• Structure: Returns: was incorrectly nested under Parameter: in four method entries (to_adi, to_pickle, read_pickle, to_excel); moved to correct sibling level
• Consistency: "Licence" → "License" to match the badge; missing blank lines added after ## Getting Started and before ## FAQ / Troubleshooting
• read_pickle return description: Added missing article "the" and removed trailing whitespace

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