Add known issue to 7.6.0 / 7.6.1 / 7.6.2 release notes for elastic#66146

 (elastic#66690) (elastic#66924)

* Add known issue for elastic#66146

* fix property name

* Apply suggestions from code review

Co-authored-by: gchaps <33642766+gchaps@users.noreply.github.com>

Co-authored-by: gchaps <33642766+gchaps@users.noreply.github.com>

Co-authored-by: Pierre Gayvallet <pierre.gayvallet@gmail.com>

docs/CHANGELOG.asciidoc

@@ -355,6 +355,15 @@ Platform::
 
 See <<breaking-changes-7.6,breaking changes in 7.6>>.
 
+[float]
+[[known-issue-7.6.2]]
+=== Known issue
+
+Configuration::
+* The `server.customResponseHeaders` option prevents {kib} from starting if headers are set using a type other than string.
+To fix this, convert your boolean and number headers to strings. For example, use`my-header: "true"` instead of `my-header: true`.
+{issue}66146[#66146]
+
 [float]
 [[bug-7.6.2]]
 === Bug fixes
@@ -397,6 +406,15 @@ Visualizations::
 
 See <<breaking-changes-7.6,breaking changes in 7.6>>.
 
+[float]
+[[known-issue-7.6.1]]
+=== Known issue
+
+Configuration::
+* The `server.customResponseHeaders` option prevents {kib} from starting if headers are set using a type other than string.
+To fix this, convert your boolean and number headers to strings. For example, use `my-header: "true"` instead of `my-header: true`.
+{issue}66146[#66146]
+
 [float]
 [[security-fix-7.6.1]]
 === Security issues
@@ -479,6 +497,9 @@ See also <<breaking-changes-7.6,breaking changes in 7.6>>.
 === Known issue
 
 * When you use the default `dateFormat:tz: browser` setting, the timestamps appear in UTC instead of the local time of the user browser. To use the local time of the user browser, set `dateFormat:tz:` to the timezone of the user. {issue}57457[#57457]
+* The `server.customResponseHeaders` option prevents {kib} from starting if headers are set using a type other than string.
+To fix this, convert your boolean and number headers to strings. For example, use `my-header: "true"` instead of `my-header: true`.
+{issue}66146[#66146]
 
 [float]
 [[enhancement-7.6.0]]