fix(description): open builtin description

Remove empty section tag and add descriptions

Author: BenIsenstein

Diff for: docs/builtin/open.md

@@ -19,9 +19,19 @@ Python open() built-in function
 ## Examples
 
 ```python
-f = open("some_file.txt", "r")
-```
+>>> spam = open('spam.txt', mode='x')
+>>> spam.write('My first line\n\n')
+>>> spam.close()
+# Opens a brand new file (in 'x' mode will throw if already exists)
+
+>>> with open('spam.txt', mode='a') as spam:
+...     spam.write('My second line')
+# Appends to file and automatically closes afterward
 
-<!-- remove this tag to start editing this page -->
-<empty-section />
-<!-- remove this tag to start editing this page -->
+>>> with open('spam.txt') as spam:
+...     content = spam.read()
+...     print(content)
+# My first line
+#
+# My second line
+```