[ENH] readme for local postgres setup (chroma-core#1795)

## Description of changes
per discussion, adding a local postgres setup readme doc

go/README.md

@@ -0,0 +1,15 @@
+# Set up Local Postgres
+
+- Install Postgres on Mac
+    - `brew install postgresql@14`
+- Start & Stop
+    - `brew services start postgresql`
+    - `brew services stop postgresql`
+- create testing db
+    - terminal: `psql postgres`
+    - postgres=# `create role chroma with login password 'chroma';`
+    - postgres=# `alter role chroma with superuser;`
+    - postgres=# `create database chroma;`
+- Atlas schema migration
+    - [~/chroma/go]: `atlas migrate diff --env dev`
+    - [~/chroma/go]: `atlas --env dev migrate apply --url "postgres://chroma:chroma@localhost:5432/chroma?sslmode=disable"`