docs: align CONTRIBUTING with canonical template (#137)

Author: joshiste

CONTRIBUTING.md

@@ -1,5 +1,15 @@
 # Contributing
 
+## Prerequisites
+
+To build and run this extension locally, you need:
+
+- [Go](https://go.dev/dl/) 1.26 or later
+- [GNU Make](https://www.gnu.org/software/make/)
+- [GoReleaser](https://goreleaser.com/) (used by `make build`)
+- [Docker](https://www.docker.com/) (required for `make container` and container-based tests)
+- [Helm](https://helm.sh/docs/intro/install/) and [helm-unittest](https://github.com/helm-unittest/helm-unittest) (for chart development; `make charttesting` and `make chartlint`)
+
 ## Getting Started
 
 1. Clone the repository
@@ -9,14 +19,15 @@
 
 ## Tasks
 
-The `Makefile` in the project root contains commands to easily run common admin tasks:
+The `Makefile` in the project root contains commands to easily run common admin tasks. Run `make help` to list all available targets.
 
-| Command        | Meaning                                                                                               |
-|----------------|-------------------------------------------------------------------------------------------------------|
-| `$ make tidy`  | Format all code using `go fmt` and tidy the `go.mod` file.                                            |
-| `$ make audit` | Run `go vet`, `staticheck`, execute all tests and verify required modules.                            |
-| `$ make build` | Build a binary for the extension. Creates a file called `extension` in the repository root directory. |
-| `$ make run`   | Build and then run the created binary.                                                                |
+| Command            | Meaning                                                                                               |
+|--------------------|-------------------------------------------------------------------------------------------------------|
+| `$ make tidy`      | Format all code using `go fmt` and tidy the `go.mod` file.                                            |
+| `$ make audit`     | Run `go vet`, `staticcheck`, execute all tests and verify required modules.                           |
+| `$ make build`     | Build a binary for the extension. Creates a file called `extension` in the repository root directory. |
+| `$ make run`       | Build and then run the created binary.                                                                |
+| `$ make container` | Build the container image (`extension-stackstate:latest`) using Docker buildx.                        |
 
 ## Releasing the Code/Docker Image
 
@@ -29,14 +40,14 @@ To make a new release, do the following:
 
 ## Releasing Helm Chart Changes
 
- 1. Update the version number in the [Chart.yaml](charts/steadybit-extension-stackstate/Chart.yaml)
+ 1. Update the version number in the [Chart.yaml](./charts/steadybit-extension-stackstate/Chart.yaml)
  2. Commit and push the changes.
 
 Changing the Helm chart without bumping the version will result in the following error:
 
 ```
 > Releasing charts...
-    Error: error creating GitHub release steadybit-extension-scaffold-1.0.0: POST https://api.github.com/repos/steadybit/extension-scaffold/releases: 422 Validation Failed [{Resource:Release Field:tag_name Code:already_exists Message:}]
+    Error: error creating GitHub release steadybit-extension-stackstate-1.0.0: POST https://api.github.com/repos/steadybit/extension-stackstate/releases: 422 Validation Failed [{Resource:Release Field:tag_name Code:already_exists Message:}]
 ```
 
 ## Contributor License Agreement (CLA)