[Inkscape-docs] Inkscape.org now using oauth2 for google

Dear Developers and docs, Please be aware that because google are decommissioning their openid services, we've moved the inkscape.org social auth login from openid to their oauth2 service. If you have trouble logging in using the new service, or find that when you do, you have a new account instead of your original one. Please let me know. Martin,