Add "update priority" (#2988)

## Issue Addressed

NA

## Proposed Changes

Add the "Update Priority" section which has featured in many of our previous releases (e.g., [Poñeta](https://github.com/sigp/lighthouse/releases/v2.1.1)).

Previously this section has been copied in manually.

## Additional Info

NA

.github/workflows/release.yml

@@ -232,6 +232,19 @@ jobs:
 
                   Add a summary.
 
+                  ## Update Priority
+
+                  This table provides priorities for which classes of users should update particular components.
+
+                  |User Class |Beacon Node  | Validator Client|
+                  --- | --- | ---
+                  |Staking Users| <TODO> | <TODO> |
+                  |Non-Staking Users| <TODO>|---|
+
+                  *See [Update
+                  Priorities](https://lighthouse-book.sigmaprime.io/installation-priorities.html)
+                  more information about this table.*
+
                   ## All Changes
 
                   ${{ steps.changelog.outputs.CHANGELOG }}

book/src/SUMMARY.md

@@ -11,6 +11,7 @@
     * [Raspberry Pi 4](./pi.md)
     * [Cross-Compiling](./cross-compiling.md)
     * [Homebrew](./homebrew.md)
+    * [Update Priorities](./installation-priorities.md)
 * [Key Management](./key-management.md)
     * [Create a wallet](./wallet-create.md)
     * [Create a validator](./validator-create.md)

book/src/installation-priorities.md

@@ -0,0 +1,22 @@
+# Update Priorities
+
+When publishing releases, Lighthouse will include an "Update Priority" section in the release notes. As an example, see the [release notes from v2.1.2](https://github.com/sigp/lighthouse/releases/tag/v2.1.2)).
+
+The "Update Priority" section will include a table which may appear like so:
+
+|User Class |Beacon Node  | Validator Client|
+--- | --- | ---
+|Staking Users| Medium Priority | Low Priority |
+|Non-Staking Users| Low Priority|---|
+
+To understand this table, the following terms are important:
+
+- *Staking users* are those who use `lighthouse bn` and `lighthouse vc` to stake on the Beacon Chain.
+- *Non-staking users* are those who run a `lighthouse bn` for non-staking purposes (e.g., data analysis or applications).
+- *High priority* updates should be completed as soon as possible (e.g., hours or days).
+- *Medium priority* updates should be completed at the next convenience (e.g., days or a week).
+- *Low priority* updates should be completed in the next routine update cycle (e.g., two weeks).
+
+Therefore, in the table above, staking users should update their BN in the next days or week and
+their VC in the next routine update cycle. Non-staking should also update their BN in the next
+routine update cycle.