docs: add the main README

Dockerfile

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-FROM golang:1.26.0 AS build
+FROM golang:1.26.0-alpine AS build
 
 WORKDIR /workspace
 

README.md

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 # Cert Manager DeSEC Webhook
 
+<p>
+  <img src="https://raw.githubusercontent.com/cert-manager/cert-manager/d53c0b9270f8cd90d908460d69502694e1838f5f/logo/logo-small.png" height="256" width="256" alt="cert-manager project logo" />
+</p>
+
+# Independently maintained ACME webhook for desec.io DNS API
+
+This solver can be used with [desec.io](https://desec.io) DNS API. The documentation of the API can be found [here](https://desec.readthedocs.io/en/latest/)
+
+## Requirements
+- [go](https://golang.org) => 1.26.0
+- [helm](https://helm.sh/) >= v3.0.0
+- [kuberentes](https://kubernetes.io/) => 1.25.0
+- [cert-manager](https://cert-manager.io/) => 1.19.0
+
+## Installation
+
+### Using helm from local checkout
+```bash
+helm install \
+  -n cert-manager \
+  desec-webhook \
+  charts/cert-manager-desec-webhook
+```
+
+### Using public helm chart
+```bash
+helm install \
+  -n cert-manager \
+  --version <release without leading "v"> \
+  desec-webhook \
+  oci://ghcr.io/pr0ton11/charts/cert-manager-desec-webhook
+```
+
+## Uninstallation
+
+## Creating an issuer
+
+Create a secret containing the credentials
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: desec-io-token
+  namespace: cert-manager
+type: Opaque
+data:
+  token: your-key-base64-encoded
+```
+
+We can also then provide a standardised 'testing framework', or set of
+conformance tests, which allow us to validate that a DNS provider works as
+expected.
+Create a 'ClusterIssuer' or 'Issuer' resource as the following:
+
+```yaml
+apiVersion: cert-manager.io/v1
+kind: ClusterIssuer
+metadata:
+  name: letsencrypt-staging
+spec:
+  acme:
+    server: https://acme-staging-v02.api.letsencrypt.org/directory
+    email: mail@example.com
+
+    privateKeySecretRef:
+      name: letsencrypt-staging
+
+    solvers:
+      - dns01:
+          webhook:
+            config:
+              apiKeySecretRef:
+                key: token
+                name: desec-io-token
+            groupName: acme.pr0ton11.github.com
+            solverName: desec
+```
+
+## Create a manual certificate
+
+```yaml
+apiVersion: cert-manager.io/v1
+kind: Certificate
+metadata:
+  name: example-cert
+  namespace: cert-manager
+spec:
+  commonName: example.com
+  dnsNames:
+    - example.com
+  issuerRef:
+    name: letsencrypt-staging
+    kind: ClusterIssuer
+  secretName: example-cert
+```
+
+## Using cert-manager with traefik ingress
+```yaml
+
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: bitwarden
+  namespace: utils
+  labels:
+    app: bitwarden
+  annotations:
+    cert-manager.io/cluster-issuer: letsencrypt-staging
+    kubernetes.io/ingress.class: traefik
+    traefik.ingress.kubernetes.io/rewrite-target: /$1
+    traefik.ingress.kubernetes.io/router.entrypoints: websecure
+    traefik.ingress.kubernetes.io/router.tls: 'true'
+spec:
+  tls:
+    - hosts:
+        - bitwarden.acme.example.com
+      secretName: bitwarden-crt
+  rules:
+    - host: bitwarden.acme.example.com
+      http:
+        paths:
+          - path: /
+            pathType: Prefix
+            backend:
+              service:
+                name: bitwarden
+                port:
+                  number: 80
+
+```
+
+### Creating your own repository
+
+### Running the test suite
+
+All DNS providers **must** run the DNS01 provider conformance testing suite,
+else they will have undetermined behaviour when used with cert-manager.
+
+Provide a secret.yaml in testdata/desec
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: desec-token
+data:
+  token: your-key-base64-encoded
+type: Opaque
+```
+
+Define a **TEST_ZONE_NAME** matching to your authenticaton creditials.
+
+```bash
+$ TEST_ZONE_NAME=example.com. make test
+```