给定一组英文文本，将其中所有的字符转化为小写字母，并计算每个单词在文本中出现的次数。
Text: Welcome to the world of programming. Programming is a fun way to learn.
Input:
welcome to the world of programming. programming is a fun way to learn.

Output:

welcome: 1
to: 1
the: 1
world: 1
of: 1
programming: 2
is: 1
a: 1
fun: 1
way: 1
learn: 1