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

tldr/echo

@@ -0,0 +1,33 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# echo
+
+> Print given arguments.
+> More information: <https://www.gnu.org/software/coreutils/echo>.
+
+- Print a text message. Note: quotes are optional:
+
+`echo "{{Hello World}}"`
+
+- Print a message with environment variables:
+
+`echo "{{My path is $PATH}}"`
+
+- Print a message without the trailing newline:
+
+`echo -n "{{Hello World}}"`
+
+- Append a message to the file:
+
+`echo "{{Hello World}}" >> {{file.txt}}`
+
+- Enable interpretation of backslash escapes (special characters):
+
+`echo -e "{{Column 1	Column 2}}"`
+
+- Print the exit status of the last executed command (Note: In Windows Command Prompt and PowerShell the equivalent commands are `echo %errorlevel%` and `$lastexitcode` respectively):
+
+`echo $?`