Using the lesson02_example.html file as a template
(i.e., a starting point to modify), create an HTML page in which you can
"encode" and "decode" a message using a substitution cipher.
So, in the page you will have a textarea to input your text, one textarea to
show the result (encoded or decoded), and three buttons: to encode,
decode or clear the textareas.
The substitution cipher should do a char shift of +7 values. So, when you encode the string "abc" you should get "hij". When encoding "{Hello!!!}", you should get "$Olssv(((&".
To get the char code from the first char in a string, in JavaScript use
the function .charCodeAt(0).
To convert from char code x to string, use String.fromCharCode(x).
Note: be careful to consider only chars in the range 33-126. Chars outside
such range should be ignored, i.e. kept the same.
To avoid overflows (i.e., a value that goes above 126), you will need to use
the module operator %.
Solutions to this exercise can be found under the
solutions/02 folder.