[build]: Replace node_modules with a single-file bundle produced by…

… `ncc`

Detailed description of changes:

* Update the `build` script in `package.json` so that it builds and
  "links" the TypeScript code along with all of its (transitive)
  dependencies in a single `index.js` file using `@vercel/ncc`.

* Add / copy `scripts/{Invoke-7zdec.ps1,externals/7zdec.exe}` from
  `node_modules/@actions/tool-cache/scripts` as its needed by the
  aforementioned dependency on Windows and it used to be included in the
  `node_modules` folder which will be deleted by the next commit.

* Change the `main` file in `package.json` and `action.yml` to
  `dist/index.js`. `ncc` allows only the out dir can be specified - the
  filename is always `index.js`.

* Add `lib/` and `dist/*` to .gitingore, but exclude `dist/index.js`
  from the list so it will be committed.

* Delete the `lib/` folder

* `node_modules` will be deleted in the next commit to make make the
  reviewing easier.

* Add the `dist/index.js` file produced by running `npm run build`.

* Add a `.gitattributes` file in order to set mark `dist/**` as
  `binary` for git diff and merge purposes. A wildcard is used as a
  sourcemap file could also be included later if necessary, which should
  also be considered a "binary" file.

* Update `.gitignore` to the latest version from here:
  `https://github.com/github/gitignore/blob/master/Node.gitignore`

* Set the `target` in `tsconfig.json` to `es2017`, which is [supported by
  current Node.js version - v12][1], as should make for cleaner generated
  "down-leveled" code as it has native async/await support

[1]: https://node.green/

.gitattributes

@@ -0,0 +1,8 @@
+# Mark .pnp.cjs as binary to prevent git from trying to merge it
+/dist/**                binary linguist-generated
+/.pnp.*                 binary linguist-generated
+/.yarn/releases/**      binary linguist-generated
+
+# Set the language for these files to json5 to ensure GitHub doesn't show the comments as errors
+/.vscode/*.json         linguist-language=JSON5
+tsconfig.json           linguist-language=JSON5

.gitignore

@@ -1,4 +1,7 @@
 __tests__/runner/*
+lib/
+dist/*
+!dist/index.js
 
 # Rest pulled from https://github.com/github/gitignore/blob/master/Node.gitignore
 # Logs
@@ -41,10 +44,11 @@ bower_components
 build/Release
 
 # Dependency directories
+node_modules/
 jspm_packages/
 
-# TypeScript v1 declaration files
-typings/
+# Snowpack dependency directory (https://snowpack.dev/)
+web_modules/
 
 # TypeScript cache
 *.tsbuildinfo
@@ -55,6 +59,12 @@ typings/
 # Optional eslint cache
 .eslintcache
 
+# Microbundle cache
+.rpt2_cache/
+.rts2_cache_cjs/
+.rts2_cache_es/
+.rts2_cache_umd/
+
 # Optional REPL history
 .node_repl_history
 
@@ -70,13 +80,21 @@ typings/
 
 # parcel-bundler cache (https://parceljs.org/)
 .cache
+.parcel-cache
 
-# next.js build output
+# Next.js build output
 .next
+out
 
-# nuxt.js build output
+# Nuxt.js build / generate output
 .nuxt
 
+# Gatsby files
+.cache/
+# Comment in the public line in if your project uses Gatsby and not Next.js
+# https://nextjs.org/blog/next-9-1#public-directory-support
+# public
+
 # vuepress build output
 .vuepress/dist
 
@@ -88,3 +106,16 @@ typings/
 
 # DynamoDB Local files
 .dynamodb/
+
+# TernJS port file
+.tern-port
+
+# Stores VSCode versions used for testing VSCode extensions
+.vscode-test
+
+# yarn v2
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+.pnp.*

action.yml

@@ -11,4 +11,4 @@ inputs:
     required: false
 runs:
   using: "node12"
-  main: "lib/main.js"
+  main: "dist/index.js"