Documentation update

[resiliencetheatre]

Update documentation about requirements.

Noticed that given requirements are bit low for today's planet content. Might be useful for others to reference this.

My hardware is:

• AMD Ryzen 7 5800X 8-Core Processor
• 32 GB RAM
• OS: Fedora 37

Details of successful run:

• RAM was just barely enough, I ended up with OOM killed Gnome desktop but luckily run 'sequentially-generate-planet-mbtiles--unix-amd64-v3.1.0' on tmux session where I was able to reconnect after DM restarts.
• Disk space required was around 400 GB. I spared 1 TB SSD for the job and it was enough.
• Time consumed was around 12 to 15 hours.

Result:

planet.mbtiles, size: 86 GB

Hope this helps and could be useful for documentation update.