Introduce PNPM as a package manager

[andrea-smiesna]

Closes #153

• replace npm with pnpm in scripts
• update the docs
• remove npm-audit lib, replace with pnpm audit
• update the github actions, install pnpm
• update the Dockerfile files

The architectural decision/why we chose to replace an npm package manager by pnpm:

Content-Addressable Storage System:

• A content-addressable storage system stores data in a way that each piece of data is referenced by its content (usually a hash) rather than its location.

The practical impact:

• Reduced Redundancy: since our project has multiple dependencies that rely on the same sub-dependency, pnpm will store only one copy of that sub-dependency
• Efficient Storage: this method reduces the overall amount of disk space used, as identical sub-dependencies are not redundantly stored multiple times within our project's node_modules directory

Symbolic links:

• Symbolic links (symlinks) are pointers that act as references to files or directories located elsewhere in the filesystem

The practical impact:

• Faster Installations: Symlinking is faster than copying files, so installations are quicker.
• Less Disk Space Usage: Since the actual data is stored only once globally, the node_modules directory is much smaller, containing only symlinks rather than full copies of each package and sub-dependency
• Simplified Updates: Updating a package in the global store automatically updates the symlinked references in our project's node_modules, ensuring consistency and reducing the risk of version conflicts