chore(readme): make readme more generic (#25)

### Summary

Since we are making this example app public, the instructions
for setting up, building, and flashing are now in the readme.

### Test Plan

Verified visually.

README.md

@@ -1,4 +1,71 @@
-# WeFault Thingy91 Fleet Quickstart
+# Thingy91 Example App
 
-This application is currently being used to test the WeFaultThingy91 fleet.
-See the Notion page [WeFault Thingy91 Fleet Quickstart](https://www.notion.so/memfault/WeFault-Thingy91-Fleet-Quickstart-394ab5bd97ab4a49af86f40423f51982?pvs=4) for the latest information on joining the fleet as well as building this app and flashing a device.
+This application is based on the Nordic Asset Tracker app which can be found in
+NCS under `applications/asset_tracker_v2`. This specific app was forked from
+[the out-of-tree version of this application](https://github.com/NordicSemiconductor/asset-tracker-cloud-firmware-aws).
+
+## Setup
+
+Follow the [Getting Started with the Thingy91](https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/device_guides/working_with_nrf/nrf91/thingy91_gsg.html)
+instructions for updating the modem firmware, activating the SIM card, and
+registering the device with nRF Cloud.
+
+Install Zephyr's dependencies [here](https://docs.zephyrproject.org/latest/develop/getting_started/index.html).
+
+Create a workspace folder:
+
+```bash
+mkdir ~/thingy91-workspace
+cd thingy91-workspace
+```
+
+Create and activate a virtual environment:
+
+```bash
+python3 -m venv .venv
+source .venv/bin/activate
+```
+
+Install west, Zephyr's meta-tool:
+
+```bash
+pip install west
+```
+
+Use west to initialize the workspace with our asset-tracker repo as the
+manifest repo and then update the modules from the manifest
+`memfault-asset-tracker/west.yml`:
+
+```bash
+cd ~/thingy91-workspace
+west init -m [email protected]:memfault/memfault-asset-tracker
+west update
+```
+
+Install Python requirements for both Zephyr and NCS:
+
+```bash
+pip install -r zephyr/scripts/requirements.txt -r nrf/scripts/requirements-build.txt
+```
+
+## Build & Flash
+
+Build the app with your project key and the Memfault overlay:
+
+```bash
+cd ~/thingy91-workspace
+west build -b thingy91_nrf9160_ns -p always memfault-asset-tracker -- \
+-DCONFIG_MEMFAULT_NCS_PROJECT_KEY=\"${MEMFAULT_PROJECT_KEY}\" \
+-DOVERLAY_CONFIG=overlay-memfault.conf
+```
+
+Flash:
+
+```bash
+west flash --erase
+```
+
+## Deploying OTAs
+
+This app also has an example of how to auto-deploy releases with Memfault.
+See [`ota-deploy.yml`](.github/workflows/ota-deploy.yaml).

west.yml

@@ -6,10 +6,10 @@ manifest:
   projects:
     - name: sdk-nrf
       path: nrf
-      # Symlinking to a local version doesn't play nice
-      # with west, so instead point to our fork for now
-      # TODO: Remove url and revision when this is no
-      # longer needed
+      # We point to a branch on the Memfault fork of
+      # NCS, which may have beta NCS changes for
+      # Memfault currently under testing, but will
+      # otherwise be a mirror of upstream NCS main.
       url: https://github.com/memfault/sdk-nrf.git
       revision: dogfood
       import: true