Pyprojectx

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Bug Fixes
- 98 existing tool virtual environment is reused even if pw.lock changed

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Bug Fixes
- 96 fix locking of pyprojectx's own dependencies

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Bug Fixes
- 90 fix PowerShell activate script when symlinks are allowed on Windows

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Features & Improvements
- use an informative prompt when activating a tool context virtual environment

Bug Fixes
- 90 activate script doesn't work in windows PowerShell

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Bug Fixes
- 90 activate script doesn't work on cygwin

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Features & Improvements
- update pip when installing a tool context virtual environment

Bug Fixes
- 90 activate script seems to be broken on windows
- 91 crashes on windows when symlinks are not allowed

Documentation
- fixed windows development instructions in README.md