Fix documentation path exports and other little things

[airswing]

Description

Modified the README.md to make exporting paths work after cding into the agave-cli directory. Fixed git command and other small things like formatting in shell blocks and spelling.
Fixed a spelling error in auth.rst

#94

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Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have signed-off my commits with git commit -s
• I have added tests to cover my changes.
• All new and existing tests passed.