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

tldr/ifne

@@ -0,0 +1,17 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# ifne
+
+> Run a command depending on the emptyness of `stdin`.
+> More information: <https://joeyh.name/code/moreutils/>.
+
+- Run the specified command if and only if `stdin` is not empty:
+
+`ifne {{command options ...}}`
+
+- Run the specified command if and only if `stdin` is empty, otherwise pass `stdin` to `stdout`:
+
+`ifne -n {{command options ...}}`