[SC64] Revise README to include Feature subheadings for easy at-a-glance reading (#77)

I made some minor changes to the README to try and address the most
common read-the-manual moments seen in the N64Brew Discord.

Specifically, I broke out the features listed in the README into
sub-categories, with the non-developer features up at the top for
non-technical people to read first.

The categories are:
- Hardware-Dependent Game Features
- Game Saves
- Menu
- Game Development
- Cartridge Production

Co-authored-by: Mateusz Faderewski <sc@mateuszfaderewski.pl>

README.md

@@ -4,25 +4,40 @@
 **For non-technical description of the SummerCart64, please head to the https://summercart64.dev website!**
 
 ## Features
- - 64 MiB SDRAM memory for game and save data
+
- - 16 MiB FLASH memory for bootloader and extended game data
+ - **ROM and Save Memory On-board**
- - 8 kiB on-chip buffer for general use
+   - 64 MiB SDRAM memory for game and save data (enough memory to support every retail game without compromise)
- - ~23.8 MiB/s peak transfer rate USB interface for data upload/download and debug functionality
+   - 16 MiB FLASH memory for bootloader and extended game data (with extended memory flashcart supports game ROMs up to 78 MiB)
- - ~23.8 MiB/s peak transfer rate SD card interface
+
- - EEPROM, SRAM and FlashRAM save types with automatic writeback to SD card
+ - **Game Saves**
- - Battery backed real time clock (RTC)
+   - EEPROM 4k/16k, SRAM and FlashRAM save types with an automatic writeback to the SD card (no reset button press required)
- - Status LED and button for general use
+
+ - **Hardware-Dependent Game Features**
    - 64DD add-on emulation
- - IS-Viewer 64 debug interface
+   - Battery backed real time clock (RTC)
- - N64 bootloader with support for IPL3 registers spoofing and loading menu from SD card
+
+ - **Menu**
    - Dedicated open source menu written specifically for this flashcart - [N64FlashcartMenu](https://github.com/Polprzewodnikowy/N64FlashcartMenu)
- - Enhanced [UltraCIC_C](https://github.com/jago85/UltraCIC_C) emulation with automatic region switching and programmable seed/checksum values
+
- - PC app for communicating with flashcart (game/save data upload/download, feature enable control and debug terminal)
+ - **Game Development**
- - Access to the SD card via USB interface with the use of the PC app
+   - ~23.8 MiB/s peak transfer rate SD card interface
+   - ~23.8 MiB/s peak transfer rate USB interface for data upload/download and debug functionality
+   - PC app to access the flashcart features:
+     - Game/save data upload/download
+     - Feature enable control
+     - Debug terminal
+     - Access to the SD card
+     - Firmware update
    - [UNFLoader](https://github.com/buu342/N64-UNFLoader) support
- - Initial programming via UART header or dedicated JTAG/SWD interfaces
+   - IS-Viewer 64 debug interface (fixed 64 kiB buffer with a movable base address)
- - Software and firmware updatable via USB interface
+   - 8 kiB on-chip buffer for general use
- - 3D printable plastic shell
+   - Status LED and button for general use
+   - [UltraCIC_C](https://github.com/jago85/UltraCIC_C) emulation with automatic region switching and programmable seed/checksum values
+   - N64 bootloader with support for IPL3 registers spoofing and loading menu from SD card
+
+ - **Cartridge Production**
+   - Initial programming via UART header or via dedicated JTAG/SWD interfaces
+   - 3D printable shell
 
 ---