added a transfer.sh plugin (#5854)

* added a transfer.sh plugin
created a function to easily upload files to transfer.sh file sharing site
Usage : transfer file.txt

* added README for transfer.sh plugin

* replaced transfer function with @nl5887 version

* updated transfer README.md

* modified the script to use tar command instead of zip

* Update README formatting
Co-authored-by: Remco Verhoef <remco@dutchcoders.io>

plugins/transfer/README.md

+# `transfer` plugin
+
+[`transfer.sh`](https://transfer.sh) is an easy to use file sharing service from the command line
+
+## Usage
+
+Add `transfer` to your plugins array in your zshrc file:
+```zsh
+plugins=(... transfer)
+```
+
+Then you can:
+
+- transfer a file:
+
+```zsh
+transfer file.txt
+```
+
+- transfer a whole directory (it will be automatically compressed):
+
+```zsh
+transfer directory/
+```

plugins/transfer/transfer.plugin.zsh

+# transfer.sh Easy file sharing from the command line
+# transfer Plugin
+# Usage Example :
+# > transfer file.txt
+# > transfer directory/
+
+
+
+# Author:
+#   Remco Verhoef <remco@dutchcoders.io>
+#   https://gist.github.com/nl5887/a511f172d3fb3cd0e42d
+#   Modified to use tar command instead of zip
+#
+
+curl --version 2>&1 > /dev/null
+if [ $? -ne 0 ]; then
+  echo "Could not find curl."
+  return 1
+fi
+
+transfer() { 
+    # check arguments
+    if [ $# -eq 0 ]; 
+    then 
+        echo "No arguments specified. Usage:\necho transfer /tmp/test.md\ncat /tmp/test.md | transfer test.md"
+        return 1
+    fi
+
+    # get temporarily filename, output is written to this file show progress can be showed
+    tmpfile=$( mktemp -t transferXXX )
+    
+    # upload stdin or file
+    file=$1
+
+    if tty -s; 
+    then 
+        basefile=$(basename "$file" | sed -e 's/[^a-zA-Z0-9._-]/-/g') 
+
+        if [ ! -e $file ];
+        then
+            echo "File $file doesn't exists."
+            return 1
+        fi
+        
+        if [ -d $file ];
+        then
+            echo $file
+            # tar directory and transfer
+            tarfile=$( mktemp -t transferXXX.tar.gz )
+            cd $(dirname $file) && tar -czf $tarfile $(basename $file)
+            curl --progress-bar --upload-file "$tarfile" "https://transfer.sh/$basefile.tar.gz" >> $tmpfile
+            rm -f $tarfile
+        else
+            # transfer file
+            curl --progress-bar --upload-file "$file" "https://transfer.sh/$basefile" >> $tmpfile
+        fi
+    else 
+        # transfer pipe
+        curl --progress-bar --upload-file "-" "https://transfer.sh/$file" >> $tmpfile
+    fi
+   
+    # cat output link
+    cat $tmpfile
+
+    # cleanup
+    rm -f $tmpfile
+}
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