Broken links in documentation

[SallSim]

In this issue we list broken links that need to be fixed in documentation for Castor release.

Page: https://github.com/tillitis/tillitis-key1/blob/main/doc/toolchain_setup.md#gateware-yosysicestorm-toolchain

• IceStorm link
• Reference to http://bygone.clairexen.net/icestorm/

Update:
Change all URL's from http://bygone.clairexen.net/icestorm/ to https://prjicestorm.readthedocs.io/en/latest/overview.html

[mchack-work]

At the top of that document:

NOTE: Documentation migrated to dev.tillitis.se, this is kept for >history. This is likely to be outdated.

I suggest we check the Dev Handbook if everything is covered, update it if it isn't, and then remove this file.

For most of it, it should probably be OK to refer to the tkey-builder image.