Upgrade to atleast Next.js 12.2 (Current: 12.1.6)

[soumitradev]

Eventually, we have to move to Next.js 13, to avoid eventual deprecation. In Next.js 12, SWC (https://swc.rs/) was introduced, which claims to make page builds much faster than the current JS compiler (Babel). Future versions of Next.js will continue to support SWC better, which is why it is a no-brainer to move to it. It will lower build times significantly, speeding up dev, and also reducing server costs (esp. Netlify).

However, the current build system uses a Babel plugin, called "istanbul". I haven't looked too much into it, but it seems to be there to help test the code. To preserve the same build system, we will need to use the same plugin for SWC. There is a plugin available, that does the same job for SWC: https://github.com/kwonoj/swc-plugin-coverage-instrument. However, SWC plugins were only introduced in Next.js 12.2 as experimental. To move to SWC without breaking anything, we must upgrade to atleast Next.js 12.2.

Since an upgrade to a newer version of Next.js is inevitable, we should probably make the move to SWC and upgrade Next.js simultaneously.