Update cheatsheets

tldr/pgcli

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+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# pgcli
+
+> A modern PostgreSQL CLI with auto-completion and syntax highlighting.
+> More information: <https://www.pgcli.com>.
+
+- Connect to a PostgreSQL database using a connection string:
+
+`pgcli postgresql://{{user}}@{{host}}/{{database}}`
+
+- Connect to a database using flags:
+
+`pgcli {{[-h|--host]}} {{host}} {{[-U|--username]}} {{username}} {{[-d|--dbname]}} {{database}}`
+
+- Display help:
+
+`pgcli --help`