add tips&tricks page

[henrirosten]

add tips&tricks markdown page that would include some interesting non-obvious use-cases of sbomnix such as this: https://discourse.nixos.org/t/how-to-get-package-maintainers-of-all-installed-packages/27307/12

and this, that creates a list of fetched urls given a result symlink:

# Run sbomnix; include both buildtime and runtime dependencies: 
$ nix run github:tiiuae/sbomnix#sbomnix -- ./result --type=both

# Query the sbom for fetched urls:
$ nix-shell -p csvkit --run \
  'csvsql --verbose --query "select urls from sbom where urls != '\'''\'' " sbom.csv' \
  | tr " " "\n" | grep -v urls | sort | uniq \
  > fetch_urls.txt