Update README and CHANGELOG for upcoming release (#1696)

* Updates to README and CHANGELOG

* Update README.md

Author: aggarw13

CHANGELOG.md

@@ -1,6 +1,13 @@
 # Changelog for AWS IoT Device SDK for Embedded C
 
-## main
+## 202108.00 (August 2021)
+
+### Major Changes
+- This release introduces the refactored **[AWS IoT Fleet Provisioning](https://github.com/aws/fleet-provisioning-for-aws-iot-embedded-sdk)** library and **[AWS SigV4](https://github.com/aws/SigV4-for-AWS-IoT-embedded-sdk)** library.
+These libraries have gone through code quality checks including verification that no function has a [GNU Complexity](https://www.gnu.org/software/complexity/manual/complexity.html) score greater than 8, checks against deviations from the mandatory rules in the [MISRA coding standard](https://www.misra.org.uk), static code analysis from [Coverity statical analysis](https://scan.coverity.com/) and validation of memory safety through the [CBMC automated reasoning tool](http://www.cs.cmu.edu/~modelcheck/cbmc/).
+- [#1692](https://github.com/aws/aws-iot-device-sdk-embedded-C/pull/1692) Update the existing HTTP S3 download demo to obtain temporary credentials from [AWS IoT Credential Provider](https://docs.aws.amazon.com/iot/latest/developerguide/authorizing-direct-aws.html) and use the the new **AWS SigV4 library**  to sign HTTP requests with those credentials for authenticating with AWS S3 service.
+- [#1688](https://github.com/aws/aws-iot-device-sdk-embedded-C/pull/1688) Add Demo to showcase use of **AWS IoT Fleet Provisioning** library using the ["Provisioning by Claim"](https://docs.aws.amazon.com/iot/latest/developerguide/provision-wo-cert.html#claim-based) workflow of the Fleet Provisioning feature of AWS IoT Core.
+- [#1680](https://github.com/aws/aws-iot-device-sdk-embedded-C/pull/1670) Add new transport interface implementation using **Mbed TLS** (for TLS stack) and **corePKCS11** (for credential management).
 
 ### Minor Changes
 

README.md

@@ -15,10 +15,12 @@
         * [AWS IoT Device Defender](#aws-iot-device-defender)
         * [AWS IoT Over-the-air Update Library](#aws-iot-over-the-air-update)
         * [AWS IoT Fleet Provisoning](#aws-iot-fleet-provisioning)
+        * [AWS SigV4](#aws-sigv4)
         * [backoffAlgorithm](#backoffalgorithm)
     * [Sending metrics to AWS IoT](#sending-metrics-to-aws-iot)
 * [Versioning](#versioning)
 * [Releases and Documentation](#releases-and-documentation)
+    * [202108.00](#20210800)
     * [202103.00](#20210300)
     * [202012.01](#20201201)
     * [202011.00](#20201100)
@@ -150,6 +152,12 @@ The [AWS IoT Fleet Provisioning](https://github.com/aws/fleet-provisioning-for-a
 
 <!-- See memory requirements for the latest release [here](). -->
 
+#### AWS SigV4
+
+The [AWS SigV4](https://github.com/aws/SigV4-for-AWS-IoT-embedded-sdk) library enables you to sign HTTP requests with [Signature Version 4 Signing Process](https://docs.aws.amazon.com/general/latest/gr/signature-version-4.html). Signature Version 4 (SigV4) is the process to add authentication information to HTTP requests to AWS services. For security, most requests to AWS must be signed with an access key. The access key consists of an access key ID and secret access key.
+
+<!-- See memory requirements for the latest release [here](). -->
+
 #### backoffAlgorithm
 
 The [backoffAlgorithm](https://github.com/FreeRTOS/backoffAlgorithm) library is a utility library to calculate backoff period using an exponential backoff with jitter algorithm for retrying network operations (like failed network connection with server). This library uses the "Full Jitter" strategy for the exponential backoff with jitter algorithm. More information about the algorithm can be seen in the [Exponential Backoff and Jitter AWS blog](https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/).
@@ -219,6 +227,14 @@ For example, a second release in June 2021 would be 202106.01. Although the SDK
 
 All of the released versions of the C-SDK libraries are available as git tags. For example, the last release of the v3 SDK version is available at [tag 3.1.2](https://github.com/aws/aws-iot-device-sdk-embedded-C/tree/v3.1.2).
 
+### 202108.00
+
+<!-- [API documentation of 202108.00 release](). -->
+
+This release introduces the refactored [AWS IoT Fleet Provisioning](https://github.com/aws/fleet-provisioning-for-aws-iot-embedded-sdk) library and the new [AWS SigV4](https://github.com/aws/SigV4-for-AWS-IoT-embedded-sdk) library.
+
+Additionally, this release brings minor version updates in the [AWS IoT Over-the-Air Update](https://github.com/aws/ota-for-aws-iot-embedded-sdk) and [corePKCS11](https://github.com/FreeRTOS/corePKCS11) libraries. 
+
 ### 202103.00
 
 [API documentation of 202103.00 release](https://docs.aws.amazon.com/embedded-csdk/202103.00/lib-ref/index.html)