Scorching tweaks

[Metapyziks]

Just some tweaks I did locally since the main PR.

• Scorch with hitscan weapons too
• Make sand scorching look more like mud for better contrast with the background

https://github.com/apetavern/sbox-grubs/assets/1110904/ddb1d6e5-d67f-4b79-b227-c6d8783cab98

[trundlr]

Thanks again!