Add comments to the user and vendor pages (#10004)

* Add comments to the user and vendor pages

* Add info on helping to contribute

* Update links

* s/yaml/yml/

BUGS-AND-FEATURE-REQUESTS.md

@@ -7,4 +7,4 @@ You can report bugs and feature requests to the Istio team in one of three place
 - [Community and Governance Issues](https://github.com/istio/community/issues)
 
 For security vulnerabilities, please don't report a bug (which is public) and instead follow
-[these procedures](https://istio.io/about/security-vulnerabilities/).
+[these procedures](https://istio.io/latest/docs/releases/security-vulnerabilities/).

CONTRIBUTING.md

@@ -3,3 +3,30 @@
 So you want to hack on Istio? Yay! Please refer to Istio's overall
 [contribution guidelines](https://github.com/istio/community/blob/master/CONTRIBUTING.md)
 to find out how you can help.
+
+## Promote your company on istio.io
+
+If your company supports Istio, you can list it on our [Ecosystem page](https://istio.io/latest/about/ecosystem/).
+We have categories for *providers* (who offer hosted or managed Istio services
+to their customers), *professional services* (who offer implementation support
+or consulting for Istio) and *integrations* (commercial or open source products
+that work with Istio).
+
+To add an entry to this page, edit [data/companies.yml](data/companies.yml)
+and add your information in the `providers`, `pro_services` or `integrations`
+section, as appropriate. Please add your company logo, preferably in SVG
+format, to [static/logos](static/logos).
+
+The Istio steering committee reserves the right to remove logos of companies that
+are not demeed to be in good standing in the community.
+
+## Tell the world you're using Istio
+
+Are you running Istio in production?  List yourself on our [Case Studies](https://istio.io/latest/about/case-studies/) page.
+
+If you want to add your logo to our wall of users, add an entry to the `users`
+section in [data/companies.yml](data/companies.yml), and add your logo,
+preferably in SVG format, to [static/logos](static/logos).
+
+If you'd like to be interviewed for a full case study, please [create an issue](https://github.com/istio/istio.io/issues/new),
+and we'll be in touch!

content/en/about/case-studies/_index.md

@@ -7,4 +7,6 @@ aliases:
 doc_type: about
 type: case-studies
 sidebar_none: true
----
+---
+
+[comment]: <> (To add yourself as an Istio user, please see https://github.com/istio/istio.io/blob/master/CONTRIBUTING.md.)

content/en/about/ecosystem/index.md

@@ -12,6 +12,8 @@ aliases:
 doc_type: about
 ---
 
+[comment]: <> (To add an Istio provider, professional services consultancy or integration, please see https://github.com/istio/istio.io/blob/master/CONTRIBUTING.md.)
+
 {{< tabset category-name="ecosystem-type" class="tabset--ecosystem" forget-tab=true >}}
 
     {{< tab

data/companies.yml

@@ -1,3 +1,5 @@
+# Please see [CONTRIBUTING.md](/CONTRIBUTING.md) to learn more about editing this file.
+
 providers:
   - name: "Google Cloud's Anthos Service Mesh"
     logo: "/logos/google-cloud.png"