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

tldr/[

@@ -0,0 +1,38 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# [
+
+> Check file types and compare values.
+> Returns a status of 0 if the condition evaluates to true, 1 if it evaluates to false.
+> More information: <https://www.gnu.org/software/bash/manual/bash.html#index-test>.
+
+- Test if a given variable is equal/not equal to the specified string:
+
+`[ "${{variable}}" {{=|!=}} "{{string}}" ]`
+
+- Test if a given variable is [eq]ual/[n]ot [e]qual/[g]reater [t]han/[l]ess [t]han/[g]reater than or [e]qual/[l]ess than or [e]qual to the specified number:
+
+`[ "${{variable}}" -{{eq|ne|gt|lt|ge|le}} {{integer}} ]`
+
+- Test if the specified variable has a [n]on-empty value:
+
+`[ -n "${{variable}}" ]`
+
+- Test if the specified variable has an empty value:
+
+`[ -z "${{variable}}" ]`
+
+- Test if the specified [f]ile exists:
+
+`[ -f {{path/to/file}} ]`
+
+- Test if the specified [d]irectory exists:
+
+`[ -d {{path/to/directory}} ]`
+
+- Test if the specified file or directory [e]xists:
+
+`[ -e {{path/to/file_or_directory}} ]`