Add human arm E180, and make various improvements.

[nataliakeniganti]

A src vector for the human arm symbol (codepoint E180) has been added

Additionally, several src vectors have been modified:

• Whiten cross mark button
• Fixed color black small square
• Fixed part for couple with heart

This pull request should hopefully fully address the following issues:

• A red cross should not be used #417
• Improve: Gun/water pistol emoji #385

[b-g]

Many thanks for the improvements! Great! Just the vector path quality of the arm is not there yet, especially the lower and upper parts should look more geometric. Try to redraw those lines with fewer points, which should make them more geometric and better looking. Also the shadow seems to be slightly off around the elbow, see https://openmoji.org/styleguide/#shadow

[nataliakeniganti]

it fine thanks it merged