Move "Hints" section in all exercises to a separate file

[nik-rev]

I feel like it's too easy to accidentally peek at the hints when they are simply right there. Moving them to a new file would mean that people will have to make the conscious effort to look at the hints. I just think this makes more sense than placing them right in the README file

[thatblindgeye]

Rather than moving hints to a separate file, we should probably take stock as to whether hints are necessary for some of these files. Ideally the lesson(s) leading up to when the exercises are assigned would provide the necessary information for users, though there may be some instances where a hint is necessary to be readily viewable (e.g. if we explicitly want to tell users to use a loop if it's not clear that that is the intent).

[MaoShizhong]

Agreed with what @thatblindgeye said.
Related is #460 where I feel instead of providing String.prototype.repeat as an alternative solution, the "hint" about loops should be moved to the instructions, where a mention of the repeat method could be placed (and instructed to use loops, not that method).

Same might apply for things in other exercises. But I'd rather keep the hints in the READMEs and just evaluate what hints we have.

[eyad-alkhalidy]

The hints in the following 2 exercises easily show the algorithm to solve the problem:

• 06_repeatString
• 09_sumAll

I suggest modifying the "Hints" sections for each one as follows:

06 - repeatString

• What inputs does the function need to achieve its goal?
• How can you iteratively build up the final string, using one of the inputs to control the repetition?

09_sumAll

• How will you ensure you're summing all integers within the correct range, no matter the order of the inputs?
• Think about your sum's starting value. Then, how can you make sure every single number from the smaller input to the larger one (including both) gets added to it?

[eyad-alkhalidy]

Do you think that making the "Hints" sections collapsed by default is a good idea anyway?

If so, this can be applied using the <details> and <summary> tags as instructed by GitHub Docs here.

[nik-rev]

Those tags don't help in Markdown, where you'll see the contents anyway
And the learners will see those files from their editor

[eyad-alkhalidy]

You're right @nik-rev. The content will be visible if the file is opened normally (in the editing mode) in VS Code, not in the preview mode.

Personally, I usually read this file from GitHub where the content is rendered and easier to go through. I don't know how many learners actually read the instructions from their editor. Anyway, maybe it's better to just update what hints are provided in that section.