Installation failed - opencollective-postinstall: Permission denied

Command and Log:

```
$ npm i -g docsify-cli

/root/.nvm/versions/node/v14.15.1/bin/docsify -> /root/.nvm/versions/node/v14.15.1/lib/node_modules/docsify-cli/bin/docsify

> docsify@4.12.1 postinstall /root/.nvm/versions/node/v14.15.1/lib/node_modules/docsify-cli/node_modules/docsify
> opencollective-postinstall

sh: 1: opencollective-postinstall: Permission denied
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@~2.3.1 (node_modules/docsify-cli/node_modules/chokidar/node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@2.3.2: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})

npm ERR! code ELIFECYCLE
npm ERR! syscall spawn
npm ERR! file sh
npm ERR! errno ENOENT
npm ERR! docsify@4.12.1 postinstall: `opencollective-postinstall`
npm ERR! spawn ENOENT
npm ERR!
npm ERR! Failed at the docsify@4.12.1 postinstall script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /root/.npm/_logs/2021-03-27T09_10_53_098Z-debug.log
```

At the docsify's post-install phase in debug.log:

```
5745 silly postinstall docsify@4.12.1
5746 info lifecycle docsify@4.12.1~postinstall: docsify@4.12.1
5747 verbose lifecycle docsify@4.12.1~postinstall: unsafe-perm in lifecycle false
5748 verbose lifecycle docsify@4.12.1~postinstall: PATH: /root/.nvm/versions/node/v14.15.1/lib/node_modules/npm/node_modules/npm-lifecycle/node-gyp-bin:/root/.nvm/versions/node/v14.15.1/lib/node_modules/docsify-cli/node_modules/docsify/node_modules/.bin:/root/.nvm/versions/node/v14.15.1/lib/node_modules/docsify-cli/node_modules/.bin:/root/.nvm/versions/node/v14.15.1/lib/node_modules/.bin:/root/bin:/root/.vscode-server/bin/2b9aebd5354a3629c3aba0a5f5df49f43d6689f8/bin:/root/bin:/root/.nvm/versions/node/v14.15.1/bin:/root/.vscode-server/bin/2b9aebd5354a3629c3aba0a5f5df49f43d6689f8/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
5749 verbose lifecycle docsify@4.12.1~postinstall: CWD: /root/.nvm/versions/node/v14.15.1/lib/node_modules/docsify-cli/node_modules/docsify
5750 silly lifecycle docsify@4.12.1~postinstall: Args: [ '-c', 'opencollective-postinstall' ]
5751 info lifecycle docsify@4.12.1~postinstall: Failed to exec postinstall script
5752 timing action:postinstall Completed in 149ms
5753 verbose unlock done using /root/.npm/_locks/staging-5069969764c9560c.lock for /root/.nvm/versions/node/v14.15.1/lib/node_modules/.staging
5754 timing stage:rollbackFailedOptional Completed in 379ms
5755 timing stage:runTopLevelLifecycles Completed in 8086ms
5756 warn optional SKIPPING OPTIONAL DEPENDENCY: fsevents@~2.3.1 (node_modules/docsify-cli/node_modules/chokidar/node_modules/fsevents):
5757 warn notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@2.3.2: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
5758 verbose notsup SKIPPING OPTIONAL DEPENDENCY: Valid OS: darwin
5758 verbose notsup SKIPPING OPTIONAL DEPENDENCY: Valid Arch: any
5758 verbose notsup SKIPPING OPTIONAL DEPENDENCY: Actual OS: linux
5758 verbose notsup SKIPPING OPTIONAL DEPENDENCY: Actual Arch: x64
5759 verbose stack Error: docsify@4.12.1 postinstall: `opencollective-postinstall`
5759 verbose stack spawn ENOENT
5759 verbose stack at ChildProcess. (/root/.nvm/versions/node/v14.15.1/lib/node_modules/npm/node_modules/npm-lifecycle/lib/spawn.js:48:18)
5759 verbose stack at ChildProcess.emit (events.js:315:20)
5759 verbose stack at maybeClose (internal/child_process.js:1048:16)
5759 verbose stack at Process.ChildProcess._handle.onexit (internal/child_process.js:288:5)
5760 verbose pkgid docsify@4.12.1
5761 verbose cwd /root/Works/fst-logic-centre
5762 verbose Linux 4.15.0-91-generic
5763 verbose argv "/root/.nvm/versions/node/v14.15.1/bin/node" "/root/.nvm/versions/node/v14.15.1/bin/npm" "i" "-g" "docsify-cli"
5764 verbose node v14.15.1
5765 verbose npm v6.14.8
5766 error code ELIFECYCLE
5767 error syscall spawn
5768 error file sh
5769 error errno ENOENT
5770 error docsify@4.12.1 postinstall: `opencollective-postinstall`
5770 error spawn ENOENT
5771 error Failed at the docsify@4.12.1 postinstall script.
5771 error This is probably not a problem with npm. There is likely additional logging output above.
5772 verbose exit [ 1, true ]
```