Add Voron 2 Mellow FLYF407ZG in SPI mode; This PR will not work properly without PR #255

[GadgetAngel]

*Add Voron 2 Mellow FLYF407ZG in SPI mode, This PR will not work properly without PR #255 . It contains a link to the information in PR #255

*In Community/Electronics/ added the following:

1. GadgetAngel folder
2. images subfolder

*updated Index.md file in Community/Electronics/ to add "Voron V2 - Mellow FLYF407ZG Wiring for both SPI and UART modes" (v2_flyf407zg_wiring.md) *v2_flyf407zg_wiring.md is a parent to v2_flyf407zg_spi_wiring.md

*reused three additional files: a. flyf407zg_additional_resources.md b. flyf407zg_RaspberryPi.md c. flyf407zg_Resources.md

*added initial Removal of Jumpers diagram *added initial preparation - Set Jumpers diagram for Mellow FLYF407ZG in SPI mode *added description for Voron 2.4 wiring diagram in Mellow FLYF407ZG in SPI mode *added the heatsink diagram to remind user to ensure that the heatsinks are installed on the stepper motor drivers for: *Added the following MCU with heat sinks in SPI mode *added URL to the Klipper Configuration file by Antage (https://gist.githubusercontent.com/antage/1976d9df8e8a1126ebbe6f3935145394/raw/6bc4c53194be75a9889fba754ffa61fbb5c7cb89/printer.ini) for Mellow FLYF407ZG *informed user that the above config file by Antage needs to be changed from UART to SPI *added links to other resources