Implement secure templates

[kildom]

Right now, the templates contain code that is executed without restrictions, so it must be trusted.

By default, the template should have only limited functionality. Full node.js or Web API should be available if user allows it.

This can be done using this project (when it is finalized): https://github.com/kildom/deprecated/tree/spidermonkey-wasi

[kildom]

Other option: Use deno and start new constrained process when rendering template

Pros:

• Fast
• No need for a lot of implementation
• More API available

Cons:

• Executable is bigger (over 80MB)
• Requires two executables: one main with all permissions, second is original deno to allow restricting access to specific files at runtime.
• Is is really so secure? https://docs.deno.com/runtime/fundamentals/security/#executing-untrusted-code