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

tldr/pg_isready

@@ -0,0 +1,21 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# pg_isready
+
+> Check the connection status of a PostgreSQL server.
+> More information: <https://www.postgresql.org/docs/current/app-pg-isready.html>.
+
+- Check connection:
+
+`pg_isready`
+
+- Check connection with a specific hostname and port:
+
+`pg_isready --host={{hostname}} --port={{port}}`
+
+- Check connection displaying a message only when the connection fails:
+
+`pg_isready --quiet`