feat(docs): Chainloop quickstart (#902)

Signed-off-by: Jose I. Paris <[email protected]>

Author: jiparis

docs/docs/quickstart.md

@@ -0,0 +1,59 @@
+---
+sidebar_position: 3
+title: Quickstart
+---
+
+# Quickstart
+
+In this quickstart, we will install Chainloop and make our first attestation:
+
+1. Install Chainloop. This quick snippet will get you through the process:
+    ```bash
+    curl -sfL https://docs.chainloop.dev/install.sh | bash -s
+    ```
+    Refer to [these instructions](/getting-started/installation) for more installation options.
+
+2. Authenticate to the Control Plane via OIDC by running:
+    ```bash
+    chainloop auth login
+    ```
+    This will create a personal token that you will use in operations not related to attestations.
+
+3. Create a new Chainloop workflow.
+    ```bash
+    chainloop wf create --name mywf --project myproject
+    ```
+    Chainloop workflows represent any CI or process you might want to attest.
+    Check [this doc](/getting-started/workflow-definition)
+    for a complete explanation of Workflows and Contracts.
+    You might also want to check our [contract reference](/reference/operator/contract).
+
+4. Create API token to perform the attestation process:
+    ```bash
+    export CHAINLOOP_TOKEN=$(chainloop org api-token create --name test-api-token -o json | jq -r ".[].jwt")
+    ```
+    CHAINLOOP_TOKEN environment variable is commonly used from CI/CD scenarios, where a personal token is not available.
+    Tokens have narrower permissions, ensuring that they can only perform the operations they are granted to.
+    More information in [API tokens](/reference/operator/api-tokens#api-tokens).
+
+5. Perform an attestation:
+    
+    First, let's [initiate the attestation](/getting-started/attestation-crafting#initialization).
+    ```bash
+    chainloop att init --workflow-name mywf
+    ```
+
+    Once attestation is initiated, we can start [adding materials](/getting-started/attestation-crafting#adding-materials) to it. 
+    In this case we are adding an OCI container image.
+    Many other material types are supported, check the [updated the list](/reference/operator/contract#material-schema)
+    ```bash
+    chainloop att add --value "ghcr.io/chainloop-dev/chainloop/control-plane:latest"
+    ```
+
+    And finally [we sign and push the attestation](/getting-started/attestation-crafting#encode-sign-and-push-attestation) to Chainloop for permanent preservation.
+    ```bash
+    chainloop att push
+    ```
+    Note that, in this example, we are not specifying any private key for signing.
+    This will make the CLI to work in key-less mode, generating an ephemeral certificate,
+    signed by Chainloop CA, to ensure the trust chain, and finally using it for the signature.