adding a widget to control DeltaE in PDOS plugin

[AndresOrtegaGuerrero]

This PR solves the problem with #959
The solution is to set DeltaE[https://www.quantum-espresso.org/Doc/INPUT_PROJWFC.html#idm30] (energy grid step eV) from dos.x and projwfc.x.

Here, we also modified a bit the description of the PDOS plugin tab, plus the addition of the new widget.

By enforcing the DeltaE to be 0.01 eV we get to see the core level pdos peaks

[codecov]

Codecov Report

Attention: Patch coverage is 42.85714% with 4 lines in your changes missing coverage. Please review.

Project coverage is 67.80%. Comparing base (329e198) to head (45a0fb9).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/aiidalab_qe/plugins/pdos/model.py	33.33%	2 Missing ⚠️
src/aiidalab_qe/plugins/pdos/setting.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #966      +/-   ##
==========================================
- Coverage   67.82%   67.80%   -0.03%     
==========================================
  Files         110      110              
  Lines        6213     6218       +5     
==========================================
+ Hits         4214     4216       +2     
- Misses       1999     2002       +3     

Flag	Coverage Δ
python-3.11	67.80% <42.85%> (-0.03%)	⬇️
python-3.9	67.82% <42.85%> (-0.03%)	⬇️

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[edan-bainglass]

Very nice @AndresOrtegaGuerrero. Flawless use of the new MVC pattern 💪
Other than my one comment regarding <br> tags, LGTM!

[edan-bainglass]

Suggested change

	<b>Recommendation for Molecules and Localized Orbitals:</b><br>
	For systems involving molecules or localized orbitals, it is recommended to use a
	<b>Recommendation for Molecules and Localized Orbitals:</b>
	<br>
	For systems involving molecules or localized orbitals, it is recommended to use a

I find it a bit clearer to give <br> tags their own line 🙂

[AndresOrtegaGuerrero]

Thank you @edan-bainglass , i did the change you suggested