remove postinstall script and run setup in prepare script

[Ryang-21]

This pr addresses a bug reported in [discord (https://discord.com/channels/897514728459468821/1082043429053276190/1446310534314987632)

• The Windows environment does not allow for || true
• Removes postinstall script all together as it is not the appropriate place to run the setup script
• Moves the setup script inside the prepare script

[github-actions]

Size Change: 0 B

Total Size: 42.5 MB

ℹ️ View Unchanged

Filename	Size
dist/stellar-sdk-minimal.js	5.56 MB
dist/stellar-sdk-minimal.min.js	4.84 MB
dist/stellar-sdk-no-axios.js	5.56 MB
dist/stellar-sdk-no-axios.min.js	4.84 MB
dist/stellar-sdk-no-eventsource.js	5.8 MB
dist/stellar-sdk-no-eventsource.min.js	5.05 MB
dist/stellar-sdk.js	5.8 MB
dist/stellar-sdk.min.js	5.05 MB

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