chore: switch from yarn to pnpm package manager

[kiriyaga-txfusion]

What 💻

• Switch from yarn to pnpm package manager

Why ✋

• Space Efficiency: pnpm saves disk space by using symbolic links to share dependencies across projects.
• Faster Install Times: pnpm installs packages faster, especially in projects with many dependencies.
• Automatic Disk Space Reclamation: pnpm removes unused dependencies automatically to keep disk usage low.
• Version Locking: pnpm generates lockfiles for consistent dependency versions.
• Deterministic Builds: pnpm ensures consistent package versions across installations.
• Support for Workspaces: pnpm supports managing multiple packages within a single repository, similar to Yarn's workspaces feature.