Update README

Author: hmarr

README.md

@@ -7,38 +7,74 @@ debugging GitHub Actions.
 
 Secrets are automatically filtered in the Actions logs.
 
+**Important:** use v2.0.0 or later, as v1 was designed for the initial GitHub Actions beta, and may no longer work as expected.
+
+## Usage instructions
+
+Add a step with `- uses: hmarr/debug-action@v2.0.0` to a workflow file. Here's an example of a complete workflow file:
+
+```yaml
+name: Debug
+on: pull_request_target
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: hmarr/debug-action@v2.0.0
+```
+
+
 ## Example output (in the Actions logs)
 
 ```
--- Environment variables ----------------------------------------------
-SECRET_TOKEN=[FILTERED]
-HOSTNAME=cdca0460a2e8
-SHLVL=1
-HOME=/github/home
-GITHUB_EVENT_PATH=/github/workflow/event.json
-GITHUB_WORKFLOW=New workflow
-PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
-GITHUB_ACTION=hmarr/debug-action
-GITHUB_REPOSITORY=hmarr/some-repository
-GITHUB_WORKSPACE=/github/workspace
-GITHUB_SHA=2b337df5ad49034668adfa8f7d69120bb844eb96
-GITHUB_ACTOR=hmarr
-GITHUB_REF=refs/heads/some-branch
-PWD=/github/workspace
-GITHUB_EVENT_NAME=pull_request
------------------------------------------------------------------------
-
--- Event JSON ---------------------------------------------------------
-{
-  "action": "opened",
-  "number": 10,
-  "pull_request": {
-  ...
+▶ Environment variables
+  ACTIONS_RUNTIME_TOKEN=***
+  CI=true
+  GITHUB_ACTION=hmarrdebug-action
+  GITHUB_ACTIONS=true
+  GITHUB_ACTION_REF=v2.0.0
+  GITHUB_ACTION_REPOSITORY=hmarr/debug-action
+  GITHUB_ACTOR=hmarr
+  GITHUB_API_URL=https://api.github.com
+  GITHUB_BASE_REF=main
+  GITHUB_EVENT_NAME=pull_request_target
+  GITHUB_EVENT_PATH=/home/runner/work/_temp/_github_workflow/event.json
+  GITHUB_HEAD_REF=patch-1
+  GITHUB_JOB=build
+  GITHUB_REF=refs/heads/main
+  GITHUB_REPOSITORY=hmarr/demo
+  GITHUB_REPOSITORY_OWNER=hmarr
+  GITHUB_RUN_ID=658297586
+  GITHUB_RUN_NUMBER=15
+  GITHUB_SERVER_URL=https://github.com
+  GITHUB_SHA=a4171998f9bf51fc5b9d0283b7d5243ac28954d1
+  GITHUB_WORKFLOW=approve
+  GITHUB_WORKSPACE=/home/runner/work/demo/demo
+  HOME=/home/runner
+  INPUT_GITHUB-TOKEN=***
+  INVOCATION_ID=44ad8f42f5244809971260b35b889a08
+  LEIN_HOME=/usr/local/lib/lein
+  LEIN_JAR=/usr/local/lib/lein/self-installs/leiningen-2.9.5-standalone.jar
+  PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+  RUNNER_OS=Linux
+  RUNNER_TOOL_CACHE=/opt/hostedtoolcache
+  RUNNER_USER=runner
+  RUNNER_WORKSPACE=/home/runner/work/demo
+  USER=runner
+
+▶ Event JSON
+  {
+    "action": "opened",
+    "number": 20,
+    "pull_request": {
+      ...
+    }
   }
-}
------------------------------------------------------------------------
 ```
 
+That example is truncated a bit, but you get the idea.
+
 ## Development and release process
 
 Each major version corresponds to a branch (e.g. `v1`, `v2`). The latest major