Update BTC RPC Explorer with RPC Terminal Functionality

[nmfretz]

This PR adds RPC Terminal and RPC Browser functionality to BTC RPC Explorer. This is done by enabling password protection with a non-empty BTCEXP_BASIC_AUTH_PASSWORD environment variable.

Closes #569

The app only requires a password and no username, per https://github.com/janoside/btc-rpc-explorer/blob/adb80713ffea2a39fb600a3e61348dbd207bba52/.env-sample#L116-L118

...but the browser popup auth asks for both a username and password, so to avoid unnecessary confusion and instructions in the app-description to leave the username blank, I have just included a default username.

[github-actions]

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Severity	File	Description
ℹ️	btc-rpc-explorer/docker-compose.yml	Potentially using unsafe user in service "web": The default container user "root" can lead to security vulnerabilities. If you are using the root user, please try to specify a different user (e.g. "1000:1000") in the compose file or try to set the UID/PUID and GID/PGID environment variables to 1000.

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