Update whitepaper to 1.4

[gernotheiser]

Put the latest version of the seL4 whitepaper up on the web site

[github-actions]

Preview your changes here

The link checker found some issues!

Running 3 checks (Scripts, Links, Images) in ["_site"] on *.html files...


Checking 422 external links
Checking 643 internal links
Checking internal link hashes in 17 files
Ran on 61 files!


For the Links > External check, the following failures were found:

* At _site/About/index.html:174:

  External link http://trustworthy.systems/projects/TS/SMACCM/ failed: Not Found (status code 404)

* At _site/Foundation/Summit/2023/index.html:513:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/Foundation/Summit/2024/index.html:234:

  External link https://www.collinsaerospace.com/ failed (status code 403)

* At _site/Foundation/Summit/2024/index.html:599:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/Learn/index.html:121:

  External link https://docs.sel4.systems/GettingStarted.html failed (status code 404)

* At _site/news/2021.html:356:

  External link https://trustworthy.systems/projects/TS/SMACCM/ failed: Not Found (status code 404)

* At _site/news/2021.html:366:

  External link https://www.darpa.mil/program/high-assurance-cyber-military-systems failed (status code 404)

* At _site/news/2021.html:368:

  External link https://trustworthy.systems/projects/TS/SMACCM/ failed: Not Found (status code 404)

* At _site/news/2023.html:461:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/news/2023.html:462:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/news/2023.html:465:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/news/2024.html:250:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/news/2024.html:255:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/news/2024.html:275:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/news/2024.html:427:

  External link https://www.collinsaerospace.com/ failed (status code 403)

* At _site/news/index.html:249:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/news/index.html:254:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/news/index.html:274:

  External link https://www.collinsaerospace.com failed (status code 403)

* At _site/news/index.html:426:

  External link https://www.collinsaerospace.com/ failed (status code 403)


HTML-Proofer found 19 failures!
make: *** [Makefile:59: checklinks] Error 1

[gernotheiser]

The linklint failures are unrelated, the news page is full of stale links.
Note: the SMACCM page is now at https://trustworthy.systems/projects/OLD/SMACCM/

[lsf37]

Link failures are almost always unrelated to any specific PR, but someone should fix them at some point. I'll have a go that. Most of these are the Collins website rejecting the link checker as DOS attack it seems.

[lsf37]

Links should be fixed in #423

[github-actions]

Preview your changes here

[lsf37]

Fine from my side.