feat: Add Shortcuts Icons

[joshuajames-smith]

Description

Adding shift-key, backspace-keyz enter-key, up-arrow, down-arrow, left-arrow, right-arrow, help-center + keyboard-shortcut icon .svg files to style/src/assets/icons. Then add all icons to icon.ts.

closes #86
relates gliff-ai/roadmap#79

Documentation

@philhallbio will need to create a shortcuts article in the user documentation, and require these icons – but these will not need added until the whole master issue (gliff-ai/roadmap#79) is complete. Do we need a shortcuts user documentation article for now the platform CURRENTLY stands?

Checklist:

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• I have read the gliff.ai Contribution Guide.
• I have requested to pull a branch and not from main.
• I have checked all commit message styles match the requested structure.
• My code follows the style guidelines of this project.
• I have commented my code, particularly in hard-to-understand areas.
• I have performed a self-review of my own code.
• I have assigned 3 or less reviewers.
• New and existing unit tests pass locally with my changes.
• I have added tests that prove my fix is effective or that my feature works.
• My changes generate no new warnings.
• I have made corresponding changes to the documentation.
• New database changes have been committed.
• If appropriate, I have bumped any version numbers.

[joshuajames-smith]

^ ignore! github decided to fail loading the icon and clicking Try Again made two commits, but there is only one file... 🥴