Update Slack link (#2640)

* Update Slack link

to the one that actually lets you join w/o an invitation (hopefully this won't attract spam)

* Update Slack link; minor wording change to intro

Update Slack link to the URL that actually lets you join w/o an invitation (hopefully this won't attract spam)

* Update Slack URL

Use URL that actually lets you join w/o an invitation (hopefully this won't attract spam)

_includes/header.html

@@ -137,7 +137,7 @@
                                 Mail List</a>
                         </li>
                         <li>
-                            <a class="dropdown-item" href="https://obo-communitygroup.slack.com/archives/C01DP18L5GW">OBO
+                            <a class="dropdown-item" href="https://join.slack.com/t/obo-communitygroup/shared_invite/zt-1oq48ttk7-kKo0i6TwntYtAq~Jcjjg4g">OBO
                                 Community Slack channel</a>
                         </li>
                         <li>

docs/PrinciplesReviewWorkflow.md

@@ -3,7 +3,7 @@ layout: doc
 title: Principle Review Process
 ---
 
-This page describes the process for reviewing, updating, and creating [OBO Foundry Principles](http://obofoundry.github.io/principles/fp-000-summary.html) by the OBO Foundry Editorial Working Group (EWG).
+This page describes the process for reviewing, updating, and creating [OBO Foundry Principles](http://obofoundry.github.io/principles/fp-000-summary.html). Most of the steps are done by the OBO Foundry Editorial Working Group (EWG).
 
 For the following, steps 1-5 are internal to the EWG and steps 6-7 are internal to the OBO Operations Committee. 
 
@@ -14,7 +14,7 @@ For the following, steps 1-5 are internal to the EWG and steps 6-7 are internal
 5. If necessary, discuss changes made during the commenting period and finalize the text.
 6. Once the EWG agrees on a final version, a member presents the text to the OBO Foundry Operations Committee for discussion during a meeting or via the issue tracker.
 7. Once the wording is approved by OBO Operations, a member of the EWG makes a pull request reflecting the consensus of previous discussions. Note that the pull request should be marked as 'draft' if it is a new principle.
-8. For new principles or major changes to existing principles, announce the proposal on the [obo-discuss mailing list](mailto:obo-discuss@googlegroups.com) and the [obo-community #general Slack channel](https://app.slack.com/client/T01BAB621JR/C01BDKWDS91) and request public feedback.
+8. For new principles or major changes to existing principles, announce the proposal on the [obo-discuss mailing list](mailto:obo-discuss@googlegroups.com) and the [obo-community #general Slack channel](https://join.slack.com/t/obo-communitygroup/shared_invite/zt-1oq48ttk7-kKo0i6TwntYtAq~Jcjjg4g) and request public feedback.
 9. Allow a two-week commenting period on the pull request.
 10. If the feedback includes major changes or objections, re-discuss during an OBO Operations call and re-do any relevant steps indicated above.
 11. At the end of the commenting period, assuming no major changes are needed, a member of the EWG will merge the pull request (removing 'draft' status if appropriate) and thereby make the changes public.

docs/participate.md

@@ -8,7 +8,7 @@ The OBO Foundry is currently a volunteer-run organization. There are many ways t
 - Submit a bug report, question, or feature request to the [OBO Foundry issue tracker](https://github.com/OBOFoundry/OBOFoundry.github.io/issues)
 - Join the [OBO-Discuss mailing list](https://groups.google.com/forum/#!forum/obo-discuss)
 - Join the [OBO-Tools mailing list](https://groups.google.com/forum/#!members/obo-tools)
-- Participate in the [OBO Community Slack channel](https://obo-communitygroup.slack.com/archives/C01DP18L5GW)
+- Participate in the [OBO Community Slack channel](https://join.slack.com/t/obo-communitygroup/shared_invite/zt-1oq48ttk7-kKo0i6TwntYtAq~Jcjjg4g)
 - [Submit your ontology](/faq/how-do-i-register-my-ontology.html) to be considered for inclusion in the OBO Foundry
 - [Create a pull request to improve this website](/faq//how-do-i-modify-website.html)
 - Nominate yourself to [join the OBO Foundry Operations Committee](/docs/NewOBOFC.html)