Add README to doc changes

Author: dlackty

README.md

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+# Base
+
+Polydice's base docker image for Rails applications.
+
+## Variants
+
+- `x.y.z` - Standard image for running on production
+- `x.y.z-testing` - Image for testing which includes additional packages.
+
+## Versions
+
+| Version | Ruby  | Node.js | Yarn    | Bundler | pnpm  |
+|---------|-------|---------|---------|---------|-------|
+| 0.31.0  | 2.7.7 | 18.18.0 | 1.22.19 | 2.4.5   | 8.8.0 |
+| 0.30.3  | 2.7.7 | 14.21.2 | 1.22.19 | 2.4.5   |       |