Extend `andika` builtin

[gekkowrld]

• fix: Handle nil dereference in expressions
• style: Use gofmt to format the go code
• chore: Successfully seperate the builtins
• chore: Create a basic string manipulation
• style: Use gofmt to format the code

Fixes: https://github.com/NuruProgramming/Nuru/issues/81

What hasn't been done:

Check types before doing the substitution. Error checks.

[gekkowrld]

Added: Type checks Error checks Support for flags

[AvicennaJr]

These are my thoughts:

1. I am unsure as to what the pull request does exactly. Kindly explain with examples of how it was before and how it is with your changes.
2. I feel like these are too many changes for one pull request.

[AvicennaJr]

I did also test:

[gekkowrld]

These are my thoughts:

1. I am unsure as to what the pull request does exactly. Kindly explain with examples of how it was before and how it is with your changes.

It tries to implement as explained in #81 c-style formatting. The only difference being the 'characters' used. I used characters as used in swahili e.g %s for safu, %t for tungo and so on. An example:

jina = "Jabari"
matunda = ["Ndimu", "Limau", "Chungwa"]

andika("%t ana %s kwenye kikapu chake.", jina, matunda)
// Jabari ana [Ndimu, Limau, Chungwa] kwenye kikapu chake.

2. I feel like these are too many changes for one pull request.

I agree, most of the 'changes' are really the ones that were made by running gofmt -w -s .. I only focuses on a few files that directly related with andika function.

[gekkowrld]

Should have string manipulation instead