doc: scripts to run embedmd on markdown files

This will help keep READMEs in sync with code.

Also adds a README for the add example.

Updates #14

script/bootstrap

@@ -8,3 +8,6 @@ go get -u \
 # Install golangci-lint
 golangci_lint_version='v1.12.3'
 curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $GOPATH/bin ${golangci_lint_version}
+
+# embedmd required for documentation generation
+go get -u github.com/campoy/embedmd

script/doc

@@ -0,0 +1,3 @@
+#!/bin/bash -ex
+
+find . -name '*.md' | xargs embedmd -w

script/generate

@@ -8,7 +8,7 @@ post=$(go list ./... | grep -E  'avo/(examples|tests)')
 go install ./internal/cmd/avogen
 
 # Attempt to delete generated files, to prove we can recreate them.
-grep -REl 'Code generated.*DO NOT EDIT\.$' . | xargs rm -v
+grep -REl 'Code generated.*DO NOT EDIT\.$' . | grep -v '.md$' | xargs rm -v
 
 # Generate once.
 go generate -v -x ${core}
@@ -19,3 +19,6 @@ go generate -v -x ${core}
 
 # Generate dependent packages.
 go generate -v -x ${post}
+
+# Regenerate documentation.
+./script/doc