docs: add how tos for workloads on control planes, and scaling up

First set of how-tos.

Signed-off-by: Steve Francis <steve.francis@talos-systems.com>
Signed-off-by: Andrey Smirnov <andrey.smirnov@talos-systems.com>

website/content/v1.4/talos-guides/howto/_index.md

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+---
+title: "How Tos"
+weight: 30
+description: "How to guide for common tasks in Talos Linux"
+---

website/content/v1.4/talos-guides/howto/scaling-up.md

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+---
+title: "How to scale up a Talos cluster"
+description: "How to add more nodes to a Talos Linux cluster."
+aliases:
+
+---
+
+To add more nodes to a Talos Linux cluster, follow the same procedure as when initially creating the cluster:
+
+- boot the new machines to install Talos Linux
+- apply the `worker.yaml` or `controlplane.yaml` configuration files to the new machines
+
+You need the `controlplane.yaml` and `worker.yaml` that were created when you initially deployed your cluster.
+These contain the certificates that enable new machines to join.
+
+Once you have the IP address, you can then apply the correct configuration for each machine you are adding, either `worker` or `controlplane`.
+
+```bash
+  talosctl apply-config --insecure \
+    --nodes [NODE IP] \
+    --file controlplane.yaml
+```
+
+The insecure flag is necessary because the PKI infrastructure has not yet been made available to the node.
+
+You do not need to bootstrap the new node.
+Regardless of whether you are adding a control plane or worker node, it will now join the cluster in its role.

website/content/v1.4/talos-guides/howto/workers-on-controlplane.md

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+---
+title: "How to enable workers on your control plane nodes"
+description: "How to enable workers on your control plane nodes."
+aliases:
+
+---
+
+By default, Talos Linux taints control plane nodes so that workloads are not schedulable on them.
+
+In order to allow workloads to run on the control plane nodes (useful for single node clusters, or non-production clusters), follow the procedure below.
+
+Modify the MachineConfig for the controlplane nodes to add `allowSchedulingOnControlPlanes: true`:
+
+```yaml
+cluster:
+    allowSchedulingOnControlPlanes: true
+```
+
+This may be done via editing the `controlplane.yaml` file before it is applied to the controlplane nodes, by `talosctl edit machineconfig`, or by [patching the machine config]({{< relref "../configuration/patching">}}).
+
+> Note: if you edit or patch the machine config on a running control plane node to set `allowSchedulingOnControlPlanes: true`, it will be applied immediately, but will not have any effect until the next reboot.
+You may reboot the nodes via `talosctl reboot`.
+
+You may also immediately make the control plane nodes schedulable by running the below:
+
+```bash
+kubectl taint nodes --all  node-role.kubernetes.io/control-plane-
+```
+
+Note that unless `allowSchedulingOnControlPlanes: true` is set in the machine config, the nodes will be tainted again on next reboot.