chore: lowercase npm

TROUBLESHOOTING.md

@@ -8,7 +8,7 @@ This document covers some common node-sass issues and how to resolve them. You s
   - [Assertion failed: (handle->flags & UV_CLOSING), function uv__finish_close](#assertion-failed-handle-flags-&-uv_closing-function-uv__finish_close)
   - [Cannot find module '/root/<...>/install.js'](#cannot-find-module-rootinstalljs)
     - [Linux](#linux)
-  - [NPM 5](#npm-5)
+  - [npm 5](#npm-5)
 - [Glossary](#glossary)
   - [Which node runtime am I using?](#which-node-runtime-am-i-using)
   - [Which version of node am I using?](#which-version-of-node-am-i-using)
@@ -43,9 +43,9 @@ $ sudo npm install --unsafe-perm -g node-sass
 
 If this didn't solve your problem please open an issue with the output from [our debugging script](#debugging-installation-issues).
 
-### NPM 5
+### npm 5
 
-Some users upgrading from previous versions of NPM have found conflicts with old lock file formats. This may be show up as a URL instead of the actual version number when downloading the binary. EX:
+Some users upgrading from previous versions of npm have found conflicts with old lock file formats. This may be show up as a URL instead of the actual version number when downloading the binary. EX:
 
 ```console
 Downloading binary from https://github.com/sass/node-sass/releases/download/vhttps://registry.npmjs.org/node-sass/-/node-sass-4.5.3.tgz/win32-x64-57_binding.node
@@ -54,7 +54,7 @@ Cannot download "https://github.com/sass/node-sass/releases/download/vhttps://re
 HTTP error 404 Not Found
 ```
 
-The easiest way to get around this is just to cleanup the NPM files and reinstall.
+The easiest way to get around this is just to cleanup the npm files and reinstall.
 
 ```console
 rm -rf node_modules