Add stub for quickly implementing custom templates tags and filters

[k4ml]

The end result is when people create their django project using labzero, they can start adding their own custom tags and filters, with all the boilerplate already done.

[Ngazetungue]

I will create a directory called templatetags and add an empty init.py to the labzero project or under src folder.
I will also create another python file under templatetags where people will use to get started with custom template tags and filters.
This will be generated every time people create their project using labzero. This works plenty well on my project.

[k4ml]

Implement some simple tags and filters as well so people can see how it should be implemented and may also use it as a base for their own tags/filters.

[Ngazetungue]

I implemented tags. I will look at filter

[Ngazetungue]

let me know when you are happy or where to edit with tags so i can go ahead with filters