Add missing ToC entries (#178)

Author: jonas-schievink

README.md

@@ -16,32 +16,41 @@ This project is developed and maintained by the [Resources team][team].
 * [Books, blogs and training materials](#books-blogs-and-training-materials)
 * [Tools](#tools)
 * [Peripheral Access Crates](#peripheral-access-crates)
+    * [Microchip](#microchip)
     * [Nordic](#nordic)
     * [NXP](#nxp)
+    * [SiFive](#sifive)
     * [STMicroelectronics](#stmicroelectronics)
     * [Texas Instruments](#texas-instruments)
     * [MSP430](#msp430)
 * [HAL implementation crates](#hal-implementation-crates)
     * [OS](#os)
     * [Nordic](#nordic-1)
     * [NXP](#nxp-1)
+    * [SiFive](#sifive-1)
     * [STMicroelectronics](#stmicroelectronics-1)
     * [Texas Instruments](#texas-instruments-1)
     * [Espressif](#espressif)
     * [Silicon Labs](#silicon-labs)
     * [XMC](#xmc)
 * [Architecture support crates](#architecture-support-crates)
     * [ARM](#arm)
+    * [RISC-V](#risc-v)
+    * [MIPS](#mips)
 * [Board support crates](#board-support-crates)
     * [Nordic](#nordic-2)
     * [NXP](#nxp-2)
+    * [SiFive](#sifive-2)
     * [Sony](#sony)
     * [STMicroelectronics](#stmicroelectronics-2)
+    * [Texas Instruments](#texas-instruments-2)
+    * [Special Purpose](#special-purpose)
 * [Driver crates](#driver-crates)
     * [WIP](#wip)
 * [no-std crates](#no-std-crates)
+    * [WIP](#wip-1)
 * [Rust forks](#rust-forks)
-    - [AVR](#avr)
+    * [AVR](#avr)
 * [Firmware projects](#firmware-projects)
 * [License](#license)