add tile author guide for new Kiln users

README.md

@@ -14,14 +14,14 @@ Looking at an [example kiln tile](https://github.com/crhntr/hello-tile/tree/main
 To install the `kiln` CLI 
 - install with Homebrew
 
-  ```sh
+  ```shell
   brew tap pivotal-cf/kiln https://github.com/pivotal-cf/kiln
   brew install kiln
   ```
 
 - download from the [releases page](https://github.com/pivotal-cf/kiln/releases)
 
-  ```sh
+  ```shell
   export KILN_VERSION
   KILN_VERSION="$(curl -H "Accept: application/vnd.github.v3+json" 'https://api.github.com/repos/pivotal-cf/kiln/releases?per_page=1' | jq -r '.[0].name')"
   curl -L -o kiln "https://github.com/pivotal-cf/kiln/releases/download/${KILN_VERSION}/kiln-darwin-${KILN_VERSION}"
@@ -32,7 +32,7 @@ To install the `kiln` CLI
 
 - build from source
 
-  ```sh
+  ```shell
   git clone git@github.com:pivotal-cf/kiln.git
   cd kiln
   git checkout 0.60.2
@@ -41,7 +41,7 @@ To install the `kiln` CLI
 
 - copy from a Docker image (to another image)
 
-  ```sh
+  ```shell
   docker pull pivotalcfreleng/kiln:latest
   ```