Add examples to Squeezing and Displacement Embeddings

[ankit27kh]

Description of the Change:
add examples to Squeezing and Displacement Embeddings
Benefits:
better documentation
Possible Drawbacks:
none
Related GitHub Issues:
#1727 #1735

[ankit27kh]

Hi @antalszava, this should be complete.
These two were very similar; thus, I have used the same documentation for both while only changing the embedding itself.

[antalszava]

Looks good! 🚀 Applying some small suggestions, then ready to merge 🚢

[codecov]

Codecov Report

Merging #1920 (2ff4081) into master (64901ef) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1920   +/-   ##
=======================================
  Coverage   98.83%   98.83%           
=======================================
  Files         222      222           
  Lines       16979    16979           
=======================================
  Hits        16781    16781           
  Misses        198      198           

Impacted Files	Coverage Δ
pennylane/templates/embeddings/displacement.py	100.00% <ø> (ø)
pennylane/templates/embeddings/squeezing.py	100.00% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 64901ef...2ff4081. Read the comment docs.