Update document

Update document

Add interactive function `use-proxy-toggle-all-proxies`

• Add interactive function use-proxy-toggle-all-proxies

Bug fixes

• Minor mode lighter starts with space
• Define a function for minor mode lighter

Unit tests and bug fixes

• Fix bug which would consider valid proxy invalid.
• Add argument to `use-proxy-toggle-proto-proxy' to make it available in non-interactive cases.
• Add unit test.

First release with basic features

Features

• Load proxy settings from $HTTP_PROXY, $HTTPS_PROXY and $NO_PROXY envs.
• Toggle proxy by protocol.
• Toggle proxy globally or respecting $NO_PROXY.
• Provide macros use-proxy-with-custom-proxies and use-proxy-with-specified-proxies.