Add CONTRIBUTING.md to master branch

- Changed the order of “Autocorrelation Wavelet Transform” and “Stationary Wavelet Transform” to agree with the order of presentation in the next sentence and the example code.
- Add numbering to all subsections in “Examples”.

No changes in functionalities in current patch update. Only fixes and additions are made to
follow JOSS guidelines.

* Update code examples for paper/paper.md to follow syntax of v0.1.14

* Update to VERSION v0.1.15

* No changes in functionalities in current patch update. Only fixes and additions are made to
follow JOSS guidelines.

* Remove OhMyREPL and Revise from Project.toml

New release to trigger Zenodo to create a DOI.

letter size paper

Fixes to JOSS code snippets.

* Fixes to JOSS code snippets. by splitting code into multiple lines to fit into 
letter size paper

* Update to VERSION v0.1.17

Organize source code of the same purpose into a subdirectory. Eg:
```
src/ACWT.jl                     src/ACWT.jl
src/acwt_all.jl         ->      src/acwt/acwt_all.jl
src/acwt_one_level.jl           src/acwt/acwt_one_level.jl
src/acwt_utils.jl               src/acwt/acwt_utils.jl
```

- Update function documentations
- Add `ns_idwt`, `nonstd_wavemult` to be exported from module.

Updates:
- Standard form wavelet multiplication.
- Documentation for `WaveMult` module.

TODO:
- Add examples in `WaveMult` documentations.

- Added parentheses to condition evaluation in `stretchmatrix` function. This improves the
  condition evaluation process that was previously buggy and produces the wrong logical expressions.
- Added a line in `mat2sparseform_nonstd` function. Previous implementation did not produce
  the right answer.

In both `mat2sparse_nonstd` and `mat2sparse_std` functions, the line
```
maxcolnorm = (maximum ∘ mapslices)(norm, Mw, dims = 1)
```
is changed to
```
maxcolnorm = mapslices(norm, Mw, dims = 1) |> maximum
```

* Reorganize source files

Organize source code of the same purpose into a subdirectory. Eg:
```
src/ACWT.jl                     src/ACWT.jl
src/acwt_all.jl         ->      src/acwt/acwt_all.jl
src/acwt_one_level.jl           src/acwt/acwt_one_level.jl
src/acwt_utils.jl               src/acwt/acwt_utils.jl
```

* Add nonstandard transform functionalities.

* Update function documentation for nonstandard transforms

- Update function documentations
- Add `ns_idwt`, `nonstd_wavemult` to be exported from module.

* Added standard form wavelet multiplication
- Standard form wavelet multiplication.
- Documentation for `WaveMult` module.

* Add API documentation page into docs/make.jl

* Fix broadcasting of logical operators in v1.6

* Bug fixes in WaveMult module
- Added parentheses to condition evaluation in `stretchmatrix` function. This improves the
  condition evaluation process that was previously buggy and produces the wrong logical expressions.
- Added a line in `mat2sparseform_nonstd` function. Previous implementation did not produce
  the right answer.

* Added documentation to demonstrate the usage of WaveMult module.

* Add additional assert for stretchmatrix.

* Add unit tests and fix bugs that arose from it.

* Syntax change to deal with v1.6 bug
In both `mat2sparse_nonstd` and `mat2sparse_std` functions, the line
```
maxcolnorm = (maximum ∘ mapslices)(norm, Mw, dims = 1)
```
is changed to
```
maxcolnorm = mapslices(norm, Mw, dims = 1) |> maximum
```

* Change @test_warn to @test_logs for unit tests in v1.6