[docs] change titles

docs/Articles.md

@@ -1,3 +1,5 @@
+# Articles
+
 * [Open-sourcing VictoriaMetrics](https://medium.com/@valyala/open-sourcing-victoriametrics-f31e34485c2b)
 * [How we created VictoriaMetrics](https://medium.com/devopslinks/victoriametrics-creating-the-best-remote-storage-for-prometheus-5d92d66787ac)
 * [VictoriaMetrics vs TimescaleDB vs InfluxDB benchmarks on 40K unique time series](https://medium.com/@valyala/when-size-matters-benchmarking-victoriametrics-vs-timescale-and-influxdb-6035811952d4)

docs/Cluster-VictoriaMetrics.md

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-# Cluster version of VictoriaMetrics
+# Cluster version
 
 VictoriaMetrics is fast, cost-effective and scalable time series database. It can be used as a long-term remote storage for Prometheus.
 

docs/ExtendedPromQL.md

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+# Extended PromQL
+
 VictoriaMetrics supports [standard PromQL](https://prometheus.io/docs/prometheus/latest/querying/basics/)
 including [subqueries](https://prometheus.io/blog/2019/01/28/subquery-support/).
 Additionally it supports useful extensions mentioned below.

docs/FAQ.md

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+# FAQ
+
 ### What is the main purpose of VictoriaMetrics?
 
 To provide the best long-term [remote storage](https://prometheus.io/docs/operating/integrations/#remote-endpoints-and-storage) solution for [Prometheus](https://prometheus.io/).

docs/Home.md

@@ -1,4 +1,4 @@
-# VictoriaMetrics docs
+# Addendum 
 
 * [Quick start](Quick-Start)
 * [`WITH` templates playground](https://play.victoriametrics.com/promql/expand-with-exprs)

docs/Single-server-VictoriaMetrics.md

@@ -1,4 +1,4 @@
-# Single-node VictoriaMetrics
+# Single-node
 
 VictoriaMetrics is fast, cost-effective and scalable time-series database. It can be used as long-term remote storage for Prometheus.
 It is available in [binary releases](https://github.com/VictoriaMetrics/VictoriaMetrics/releases),