[Fix&Enhance&Format] On README.md about poetry install

[coolermzb3]

• I have added the correct label(s) to this Pull Request or linked the relevant issue(s)
• I have provided a description of the changes in this Pull Request
• I have added documentation for my changes and have listed relevant changes in CHANGELOG.md
• If applicable, I have added tests to cover my changes.
• I have reformatted the code using poe format
• I have checked style and types with poe lint and poe type-check
• (Optional) I ran tests locally with poe test
  (or a subset of them with poe test-reduced) ,and they pass
• (Optional) I have tested that documentation builds correctly with poe doc-build

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1. [fix] First commit is crucial, otherwise poetry fails with No arguments expected for "install" command, got "envpool". It's clear in poetry-doc that quote marks are needed.
2. [enh] Second commit is optional, I encountered this problem myself (may be due to new to poetry), so I want to remind users (who may be new to this, like me). However, I'm not sure if including this in the main README is necessary, so it's up to you whether or not to merge it.
3. [fmt] Third commit is recommended, which is a minor but meaningful formatting change (it was automatically formatted by my VSCode plugin, and I didn't notice this at first).