doc: first pass at minimal-kernel

doc/minimal-kernel.md

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+# What is a Minimal Kernel for ESM in Node.js?
+
+A minimal kernel is a subset of features that the @nodejs/modules group have agreed will be necessary for all potential iterations of our ESM implementation. It strips out any features that preclude other features 
+
+# Why build a Minimal Kernel?
+
+Having a minimal kernel creates a subset that we can build consensus on top of. It will also allow sharing features across proposals that potentially have different end goals and feature sets. Finally, reaching consensus on a minimal kernel is a win for the team, showing that we do indeed have a layer of consensus even if it is not entirely clear.
+
+# What is our minimal kernel
+
+* both browser + node need bare imports
+  - implementation to be discussed
+* we cannot have dynamic path searching
+  - requiring the full path is an issue for tooling and a long term solution is required
+  - migration strategies also have issue with this
+* common.js backwards compat
+  - createRequireFunction does
+  - import.meta.require does not fail early enough
+  - hold off on importing common.js until more progress is made on dynamic modules spec
+* .mjs will be the only way to import ESM
+  - intention is to move forward with format databases to map extensions and support multiple use cases
+* only supporting importing ESM
+  - no JSON
+  - no native modules
+  - createRequireFunction used to get these
+  - will come back with format database
+* import.meta.url
+* dynamic import
+
+# How will we get from where we are to the minimal kernel
+
+* removing importing of formats other than ESM
+  - no common.js
+  - no JSON
+  - no native modules
+  - implemented in https://github.com/nodejs/ecmascript-modules/pull/3
+* removing of dynamic path searching
+  - no extension adding
+  - no directory resolution
+    - no support for index.js
+  - still maintaining support for the main field
+  - implemented in https://github.com/nodejs/ecmascript-modules/pull/2
+* adding createRequireFunction
+  - implemented in https://github.com/nodejs/node/pull/19360