Add Windows PowerShell quick start

[musaabhasan]

Summary

• add a Windows PowerShell quick-start example to the README
• add a Windows moodle-docker-wait-for-db.cmd wrapper matching the existing Bash wait script behavior
• register the new .cmd file for CRLF line endings

Rationale

Issue #192 asks for PowerShell-oriented quick-start instructions and points out that the database wait step did not have a Windows counterpart.

Validation

• ran git diff --check
• ran cmd /c bin\moodle-docker-wait-for-db.cmd and confirmed it reports a missing MOODLE_DOCKER_DB
• ran the non-Oracle/non-MSSQL path with MOODLE_DOCKER_DB=pgsql and confirmed it exits successfully
• Docker-based MSSQL and Oracle paths were not run locally

Addresses #192.