Add a requirements_dev.txt file [unitaryhack] (#2635)

* Removed black since it will be included as part of requirements_dev.txt

* Added mention of requirements_dev.txt

* Added requirements_dev.txt

* Added entry into changelog-dev for requirements_dev.txt addition into repo

* Add pip install cmd for requirements_dev.txt

Co-authored-by: David Ittah <dime10@users.noreply.github.com>

* Fix typo, hyperlink to issue

Co-authored-by: David Ittah <dime10@users.noreply.github.com>

Co-authored-by: WingCode <thewinger94@gmail.com>
Co-authored-by: David Ittah <dime10@users.noreply.github.com>

.github/CONTRIBUTING.md

@@ -64,7 +64,7 @@ Want to help with the repository itself?  There are several different avenues fo
   ["good first issue" label](https://github.com/PennyLaneAI/pennylane/contribute).  Issues with
   this label are meant for newcomers and *should* contain fewer challenging bits.  If the issue
   ends up trickier than we assumed, you can start a conversation on the issue page or open up a
-  "Work in Progress" PR to ask for help.
+  "Work in Progress" PR to ask for help. Developers new to PennyLane can use the [requirements_dev.txt](https://github.com/PennyLaneAI/pennylane/requirements_dev.txt) file to install dependencies required for PennyLane code development. Simply run `pip install -r requirements_dev.txt` from the root of the repository.
 
 * **Documentation**- If you would like to add to our documentation or suggest
   improvements/changes, let us know or submit a pull request directly. Changes that fix rendering

doc/releases/changelog-dev.md

@@ -272,6 +272,9 @@
 * Introduced a new `is_hermitian` property to determine if an operator can be used in a measurement process.
   [(#2629)](https://github.com/PennyLaneAI/pennylane/pull/2629)
 
+* Added separate requirements_dev.txt for separation of concerns for code development and just using PennyLane.
+  [(#2635)](https://github.com/PennyLaneAI/pennylane/pull/2635)
+
 <h3>Breaking changes</h3>
 
 * The `qml.queuing.Queue` class is now removed.
@@ -357,4 +360,4 @@
 This release contains contributions from (in alphabetical order):
 
 Amintor Dusko, Chae-Yeun Park, Christian Gogolin, Christina Lee, David Wierichs, Edward Jiang, Guillermo Alonso-Linaje,
-Jay Soni, Juan Miguel Arrazola, Maria Schuld, Mikhail Andrenkov, Samuel Banning, Soran Jahangiri, Utkarsh Azad
+Jay Soni, Juan Miguel Arrazola, Maria Schuld, Mikhail Andrenkov, Samuel Banning, Soran Jahangiri, Utkarsh Azad, WingCode

requirements.txt

@@ -13,5 +13,4 @@ semantic_version~=2.6
 dask[delayed]~=2022.4.1
 autoray==0.3.1
 matplotlib~=3.5
-black>=21
 opt_einsum~=3.3

requirements_dev.txt

@@ -0,0 +1,8 @@
+pre-commit>=2.19.0
+pytest>=7.1.2
+pytest-cov>=3.0.0
+pytest-mock>=3.7.0
+pytest-xdist>=2.5.0
+flaky>=3.7.0
+pytest-forked>=1.4.0
+black>=21