Update precompiled firmware

Now RP2040 Helios compatible precompiled firmware for Litl builds is available too.

UF2 files are for RP2040 compatible chips that share a pinout with the Helios. HEX files are for 'traditional' Atmel Pro Micro chips.

• sthlmkb_litl_vial-wpmhud / sthlmkb_litl_wpmhud support vial and have a WPM graph on the OLED
• sthlmkb_litl_vial-bongocat / sthlmkb_litl_bongocat have vial support and a bongocat on the OLED
• sthlmkb_litl_vial has vial support but no support for an OLED
• sthlmkb_litl_default is the default keycap with no vial and no OLED

Litl precompiled firmware for Pro Micro

Four options for precompiled firmware for Pro Micro Litl builds:

• sthlmkb_litl_default is a default firmware with no vial or OLED support
• sthlmkb_litl_vial is a default firmware with vial support but no OLED
• sthlmkb_litl_bongocat is a default firmware with vial support and bongo cat on the OLED
• sthlmkb_litl_wpmhud is a default firmware with vial support and WPM HUD on the OLED