Add known issues section to Gerrit v3.14

Highlight the two major known issues of Gerrit v3.14:

- Issue 454695136: H2 v2 corruption upon unclean shutdown
- Issue 514817934: Download commands mixup by different users

Change-Id: I06bd7ae741b8b6bc4b46db541bb5d8cd8bbbed5d

pages/site/releases/3.14.md

diff --git a/pages/site/releases/3.14.md b/pages/site/releases/3.14.md
index c733fd4..7197cbd 100644
--- a/pages/site/releases/3.14.md
+++ b/pages/site/releases/3.14.md
@@ -227,6 +227,43 @@
    it was down before directing traffic to it.
 6. Repeat steps 2 to 6 for each of the remaining Gerrit servers.
 
+### Known issues
+
+* [Issue 454695136](https://issues.gerritcodereview.com/issues/454695136):
+Upgrade to new H2 v2 storage backend for persistent caches can cause corrupt
+cache files upon forced JVM shutdown.
+
+  The new H2 library brings multi-threaded operations, but also [one critical
+  issue](https://github.com/h2database/h2database/issues/4083), reported on cache
+  files corruptions upon Gerrit ungracefully shutdowns.
+
+* [Issue 514817934](https://issues.gerritcodereview.com/issues/514817934):
+SSH/HTTP download urls provided by the download-commans plugin show wrong userid or are
+not visible at all.
+
+  The [Change 565681](https://gerrit-review.googlesource.com/c/gerrit/+/565681)
+  has introduced a new performance improvement to the rendering of the home page
+  by caching the server info across incoming calls. The server info also contains
+  the download URLs that could be user-specific, hence introducing the regression.
+
+  The new cache introduced must be disabled, so that the server info can be
+  recalculated at every call, with the drawback of disabling also the performance
+  improvement.
+
+  Example:
+  ```
+  [cache "server_config"]
+   memoryLimit = 0
+  ```
+
+  > **NOTE**: `server_config` is a non-loading Cache; `memoryLimit = 0` relies on
+  > Caffeine's weight-based eviction (entries evicted asynchronously
+  > immediately after insertion) rather than the cleaner
+  > PassthroughLoadingCache shortcut that applies to LoadingCache instances.
+  > There is a small race window where a stale entry may be returned before
+  > async eviction, but in practice this is sufficient to mitigate this
+  > issue.
+
 ## Breaking Changes
 
 * [Change 568082](https://gerrit-review.googlesource.com/c/gerrit/+/568082):