Add date function to stdlib

[CymDeveloppement]

this PR add date function to stdlib :
date display a date with a special format with gnu date command format
https://www.gnu.org/software/coreutils/date

now return current timestamp as Num

date_add add days/month/years ... to date date_add("200-01-01", "+122 days")

date_compare compare 2 date (a/b) and return 1 if a is after b, 0 if a and b is the same date, -1 if b is after a
this function can compare 2 date with différent format.

[Mte90]

• If you use "Succeded" as output for the test you don't need the output.txt file
• We aren't using tabs for codestyle but 4 spaces
• For comments the first letter of the sentence in uppercase
• A test fails because the CI uses a different timezone

[Mte90]

The timezone now it is the same but the time is different for an hour.

[Mte90]

Can we merge it?

[CymDeveloppement]

Can we merge it?

I think so

not functional

[Ph0enixKM]

I like the idea to add date but this module will change entirely when we add enums where people will be able to easily choose values like day, month etc. This module should be marked as experimental in the documentation as it will evolve very rapidly

[Mte90]

Where we can write that is experimental in the file for the documentation?

[CymDeveloppement]

Where we can write that is experimental in the file for the documentation?
@Mte90
maybe just on top of comment like :
/// EXPERIMENTAL

[Mte90]

IF you can add that so we can merge this PR

done