Documentation for require() should be updated

[Gnimuc]

currently, the doc says:

When searching for files, require first looks in the current working directory, then looks for package code under Pkg.dir(), then tries paths in the global array LOAD_PATH.

Since this commit was merged, require() hasn't been looking in the current working directory at all.

[Sisyphuss]

And I think

This function is part of the implementation of using / import

is not accurate.

It should be "This function uses using/import as part of its implementation".

[stevengj]

@Sisyphuss, no, using/import call require.

[stevengj]

It should probably also mention #13542 (it is case-sensitive, even on case-insensitive case-preserving filesystems like Mac and Windows).