feat: enable DWARF debug info in the build by setting XCADDY_DEBUG=1

[ggicci]

Fixes: #61

Allow building a debug output by setting XCADDY_DEBUG=1 for xcaddy command.

Examples:

XCADDY_DEBUG=1 xcaddy build --with github.com/xxx/xxx=$(pwd)
XCADDY_DEBUG=1 xcaddy run

[ggicci]

How to Debug a Caddy Module under Development in VSCode

cd <your local repo>

# Build a caddy with your module and turns on debug info
XCADDY_DEBUG=1 xcaddy build --with github.com/ggicci/caddy-jwt=$( pwd ) --output ./caddy

In VSCode, create a launch.json:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Launch Caddy",
      "type": "go",
      "request": "launch",
      "mode": "exec",
      "program": "${workspaceFolder}/caddy", // the debug output of caddy
      "args": ["run", "-config=example/Caddyfile"],  // args to caddy
      "cwd": "${workspaceFolder}"
    }
  ]
}

[mholt]

Why does the entire readme need to be reformatted? Let's please just make the necessary changes.

How would this be used when running xcaddy in dev mode (i.e. not the build subcommand)? Why not use XCADDY_DEBUG env var instead that can work in both cases?

[mholt]

LGTM now, thanks for the revisions!