[DOCS] Add 7.6.1. release notes (#52874)

Adds the release notes for 7.6.1.

docs/reference/release-notes.asciidoc

@@ -6,6 +6,7 @@
 
 This section summarizes the changes in each release.
 
+* <<release-notes-7.6.1>>
 * <<release-notes-7.6.0>>
 * <<release-notes-7.5.2>>
 * <<release-notes-7.5.1>>

docs/reference/release-notes/7.6.asciidoc

@@ -1,3 +1,72 @@
+[[release-notes-7.6.1]]
+== {es} version 7.6.1
+
+Also see <<breaking-changes-7.6,Breaking changes in 7.6>>.
+
+[[bug-7.6.1]]
+[float]
+=== Bug fixes
+
+Aggregations::
+* Decode max and min optimization more carefully {pull}52336[#52336] (issue: {issue}52220[#52220])
+* Fix a DST error in date_histogram {pull}52016[#52016] (issue: {issue}50265[#50265])
+
+Audit::
+* Logfile audit settings validation {pull}52537[#52537] (issues: {issue}47038[#47038], {issue}47711[#47711], {issue}52357[#52357])
+
+CCR::
+* Fix shard follow task cleaner under security {pull}52347[#52347] (issues: {issue}44702[#44702], {issue}51971[#51971])
+
+Features/cat APIs::
+* Fix NPE in RestPluginsAction {pull}52620[#52620] (issue: {issue}45321[#45321])
+
+Features/ILM+SLM::
+* ILM fix the init step to actually be retryable {pull}52076[#52076]
+
+Features/Ingest::
+* Handle errors when evaluating if conditions in processors {pull}52543[#52543] (issue: {issue}52339[#52339])
+
+Features/Monitoring::
+* Fix NPE in cluster state collector for monitoring {pull}52371[#52371] (issue: {issue}52317[#52317])
+
+Features/Stats::
+* Switch to AtomicLong for "IngestCurrent" metric to prevent negative values {pull}52581[#52581] (issues: {issue}52406[#52406], {issue}52411[#52411])
+
+Infra/Packaging::
+* Limit _FILE env var support to specific vars {pull}52525[#52525] (issue: {issue}52503[#52503])
+
+Machine Learning::
+* Don't return inflated definition when storing trained models {pull}52573[#52573]
+* Validate tree feature index is within range {pull}52460[#52460]
+
+Network::
+* Remove seeds dependency for remote cluster settings {pull}52796[#52796]
+
+Reindex::
+* Allow comma separated source indices {pull}52044[#52044] (issue: {issue}51949[#51949])
+
+SQL::
+* Supplement input checks on received request parameters {pull}52229[#52229]
+* Fix issue with timezone when paginating {pull}52101[#52101] (issue: {issue}51258[#51258])
+* Fix ORDER BY on aggregates and GROUPed BY fields {pull}51894[#51894] (issue: {issue}50355[#50355])
+* Fix milliseconds handling in intervals {pull}51675[#51675] (issue: {issue}41635[#41635])
+* Selecting a literal from grouped by query generates error {pull}41964[#41964] (issues: {issue}41413[#41413], {issue}41951[#41951])
+
+Snapshot/Restore::
+* Fix Non-Verbose Snapshot List Missing Empty Snapshots {pull}52433[#52433]
+
+Store::
+* Fix synchronization in ByteSizeCachingDirectory {pull}52512[#52512]
+
+
+
+[[upgrade-7.6.1]]
+[float]
+=== Upgrades
+
+Authentication::
+* Update oauth2-oidc-sdk to 7.0 {pull}52489[#52489] (issue: {issue}48409[#48409])
+
 [[release-notes-7.6.0]]
 == {es} version 7.6.0