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

tldr/linux/btrfs

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+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# btrfs
+
+> A filesystem based on the copy-on-write (COW) principle for Linux.
+> Some subcommands such as `btrfs device` have their own usage documentation.
+> More information: <https://btrfs.readthedocs.io/en/latest/btrfs.html>.
+
+- Create subvolume:
+
+`sudo btrfs subvolume create {{path/to/subvolume}}`
+
+- List subvolumes:
+
+`sudo btrfs subvolume list {{path/to/mount_point}}`
+
+- Show space usage information:
+
+`sudo btrfs filesystem df {{path/to/mount_point}}`
+
+- Enable quota:
+
+`sudo btrfs quota enable {{path/to/subvolume}}`
+
+- Show quota:
+
+`sudo btrfs qgroup show {{path/to/subvolume}}`