Update README with all current dashboards

The README dashboard list had drifted from the dashboards/ directory.
Add the missing dashboards (AWS, AWS CloudWatch Metric Streams, AWS
Firehose, AWS Lambda, AWS Route53, Kubernetes, MongoDB via Vector, and
Process Memory), sort the list alphabetically, and fix the broken
PostgreSQL link (/dashboards/postgresql/ -> /dashboards/postgres/).

Author: serenachou

README.md

@@ -8,20 +8,28 @@ Automated Dashboards can be found in the `dashboards/` sub directory. Each direc
 
 - [Action Mailer](/dashboards/action_mailer/)
 - [Active Job](/dashboards/active_job/)
+- [AWS](/dashboards/aws/) (via AWS CloudWatch)
+- [AWS CloudWatch Metric Streams](/dashboards/cloudwatch/)
+- [AWS Firehose](/dashboards/firehose/)
+- [AWS Lambda](/dashboards/lambda/)
+- [AWS Route53](/dashboards/route53/)
 - [Ecto](/dashboards/ecto/)
 - [Erlang](/dashboards/erlang/)
 - [Heroku](/dashboards/heroku/)
+- [Karafka](/dashboards/karafka/)
+- [Kubernetes](/dashboards/kubernetes/)
 - [MongoDB](/dashboards/mongodb/) (via AppSignal for Ruby)
+- [MongoDB](/dashboards/mongodb_vector/) (via Vector)
 - [Next.js](/dashboards/nextjs/) (deprecated)
 - [NGINX](/dashboards/nginx/)
 - [Node.js](/dashboards/nodejs/)
 - [Oban](/dashboards/oban/)
+- [PostgreSQL](/dashboards/postgres/) (via Vector)
+- [Process Memory](/dashboards/process_memory/)
 - [Puma](/dashboards/puma/)
-- [PostgreSQL](/dashboards/postgresql/) (via Vector)
 - [Render](/dashboards/render/)
 - [Ruby VM](/dashboards/ruby_vm/)
 - [Sidekiq](/dashboards/sidekiq/)
-- [Karafka](/dashboards/karafka/)
 - [Web Vitals](/dashboards/web-vitals/)
 
 ### Validation