Add install instructions to base README and add cargo-component prere…

…quisite to example app README

Signed-off-by: Kate Goldenring <[email protected]>

README.md

@@ -1,3 +1,21 @@
 # Spin `command` Trigger
 
 This is a very simple Spin trigger that executes the WASI main function.
+
+## Installation
+
+The trigger is installed as a Spin plugin. It can be installed from a release or build.
+
+To install from a release, reference a plugin manifest from a [release](https://github.com/fermyon/spin-trigger-command/releases). For example, to install the canary release:
+
+```sh
+spin plugins install --from https://github.com/fermyon/spin-trigger-command/releases/download/canary/trigger-command.json
+```
+
+Alternatively, use the `spin pluginify` plugin to install from a fresh build. This will use the pluginify manifest (`spin-pluginify.toml`) to package the plugin and proceed to install it:
+
+```sh
+spin plugins install pluginify
+cargo build --release
+spin pluginify install
+```

example/hello-world/README.md

@@ -0,0 +1,13 @@
+# Hello World Command Spin App
+
+## Prerequisites
+
+1. Install [`cargo-component`](https://github.com/bytecodealliance/cargo-component) with a version that is compatible with WASI 0.2.0
+(at least `v0.7.0`).
+
+## Running
+
+```sh
+$ spin build --up
+Hello, world!
+```