build: Run readme generation in build (#18198)

The scripts and tools we use to generate readme contents in the repo has
never been run as part of the main build. This PR adds a step to the
build, `build:readme` which calls markdown-magic to regen the readmes
across the repo, excluding the docs folder.

There are similar scripts in the docs package. Those don't need to be
modified; they're just a little unnecessary now.

I also updated the repo-wide policy CI workflow (the one that runs on
every PR) to no longer run the root prettier script (it's now part of
the build) and runs build:readme instead. This will catch any changes
outside the client release group, since md-magic runs repo-wide.

package.json

@@ -27,6 +27,7 @@
 		"build:gendocs:client:packages": "copyfiles \"packages/**/*.api.json\" ./_api-extractor-temp/doc-models/ -e \"**/node_modules/**\" -f -V",
 		"build:gendocs:server": "concurrently \"npm:build:gendocs:server:*\"",
 		"build:gendocs:server:routerlicious": "copyfiles \"server/routerlicious/**/*.api.json\" ./_api-extractor-temp/doc-models/ -e \"**/node_modules/**\" -f -V",
+		"build:readme": "markdown-magic --files \"**/*.md\" !docs",
 		"bundle-analysis:collect": "npm run webpack:profile && flub generate bundleStats",
 		"bundle-analysis:run": "flub run bundleStats --dangerfile build-tools/packages/build-cli/lib/lib/dangerfile.js",
 		"changeset": "flub changeset add --releaseGroup client",
@@ -153,6 +154,7 @@
 		"@changesets/cli": "^2.26.1",
 		"@fluid-private/changelog-generator-wrapper": "file:tools/changelog-generator-wrapper",
 		"@fluid-tools/build-cli": "^0.26.1",
+		"@fluid-tools/markdown-magic": "file:tools/markdown-magic",
 		"@fluidframework/build-common": "^2.0.3",
 		"@fluidframework/build-tools": "^0.26.1",
 		"@fluidframework/eslint-config-fluid": "^3.1.0",
@@ -202,7 +204,8 @@
 			"build:docs": {
 				"dependsOn": [
 					"^build:docs",
-					"build:gendocs:client"
+					"build:gendocs:client",
+					"build:readme"
 				],
 				"script": false
 			},
@@ -239,6 +242,9 @@
 					"^ci:build:docs"
 				]
 			},
+			"build:readme": {
+				"dependsOn": []
+			},
 			"checks": {
 				"dependsOn": [
 					"^checks",