Move pages under tldr, lint run.sh, update docs

tldr/logstash

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# logstash
+
+> An Elasticsearch ETL (extract, transform and load) tool.
+> Commonly used to load data from various sources (such as databases and log files) into Elasticsearch.
+> More information: <https://www.elastic.co/products/logstash>.
+
+- Check validity of a Logstash configuration:
+
+`logstash --configtest --config {{logstash_config.conf}}`
+
+- Run Logstash using configuration:
+
+`sudo logstash --config {{logstash_config.conf}}`
+
+- Run Logstash with the most basic inline configuration string:
+
+`sudo logstash -e 'input {} filter {} output {}'`