Rc3

Fix - allow null values in ENVS
New - keyring command for managing secrets in OS keyring
New - keyring helper function for reading secrets from OS keyring
New - keyring_prompt helper function for reading/writing secrets from/to OS keyring

Fix - upgrade command skip .git directory

Fix - global --edit option not saving
Fix - Don't overwrite header with default if explicitly defined in the .request
New - helper functions can be used in handlebar expressions instead of env vars
New - pkce helper function to generate code_verifier & code_challenge
New - uuid helper function to generate UUID
New - prompt helper function to prompt user for input
New - secure_prompt helper function to prompt user for masked input
New - file helper function to inject --file contents into a request body/template
New - allow an array or string to be posted as a JSON request body
New - send --file option to send file contents as request body
New - send multiple requests in sequence; e.g. (rc send 1 2 3)
New - decode command to decode/display JWTs in your rc envs
New - upgrade command to upgrade schemas & files in your collection

BREAKING CHANGES (new schema required):
New - allow multiple "extracts" per request
New - allow extracting "from" response body, or verbose .response
New - allow extracting "to" current env, global env, stdout, or .response file

Fix - global --edit option not saving
Fix - Don't overwrite header with default if explicitly defined in the .request
New - helper functions can be used in handlebar expressions instead of env vars
New - pkce helper function to generate code_verifier & code_challenge
New - uuid helper function to generate UUID
New - prompt helper function to prompt user for input
New - file helper function to inject --file contents into a request body/template
New - allow an array or string to be posted as a JSON request body
New - send --file option to send file contents as request body
New - send multiple requests in sequence; e.g. (rc send 1 2 3)
New - decode command to inspect HEADER & CLAIMS for a JWT

BREAKING CHANGES:
New - allow multiple "extracts" per request & allow extracting to/from additional locations

Replace "init" command with explicit "new" and "import" commands
Update "import" to use existing dirname as collection name
Update command aliases to ignore typos
Add example of importing from a git repo
Add recursive & multiple lookups of env vars
Add --send option to request command

Small updates to pypi & pip info