move info about mapbox to step-by-step section

Author: etpinard

CONTRIBUTING.md

@@ -73,7 +73,18 @@ cd plotly.js
 npm install
 ```
 
-#### Step 2: Start the test dashboard
+#### Step 2: Setup Mapbox access token
+
+As of `v1.13.0`, plotly.js includes a [`mapbox-gl`](https://github.com/mapbox/mapbox-gl-js) integration. Creating `mapbox-gl` graphs requires an
+[`accessToken`](https://www.mapbox.com/help/define-access-token/). To make sure
+that the plotly.js test suites and devtools work properly, locate your Mapbox access
+token and run:
+
+```bash
+export MAPBOX_ACCESS_TOKEN="<your access token>" && npm run pretest
+```
+
+#### Step 3: Start the test dashboard
 
 ```
 npm start
@@ -85,7 +96,7 @@ This command bundles up the source files with source maps using
 dev plotly.js bundle update every time a source file is saved) and opens up a
 tab in your browser.
 
-#### Step 3: Open up the console and start developing
+#### Step 4: Open up the console and start developing
 
 A typical workflow is to make some modifications to the source, update the
 test dashboard, inspect and debug the changes, then repeat. The test dashboard
@@ -158,18 +169,6 @@ which shows the baseline image, the generated image, the diff and the json mocks
 
 To view the results of a run on CircleCI, download the `build/test_images/` and `build/test_images_diff/` artifacts into your local repo and then run `npm run start-image_viewer`.
 
-### Note on testing our `mapbox-gl` integration
-
-Creating `mapbox-gl` graphs requires an
-[`accessToken`](https://www.mapbox.com/help/define-access-token/). To make sure
-that mapbox image and jasmine tests run properly, locate your Mapbox access
-token and run:
-
-
-```bash
-export MAPBOX_ACCESS_TOKEN="<your access token>" && npm run pretest
-```
-
 
 ## Repo organization