Fix yarn setup

According to
https://yarnpkg.com/getting-started/qa#which-files-should-be-gitignored.

Author: f1ames

Diff for: .github/workflows/coverage.yml

@@ -14,6 +14,7 @@ jobs:
     - uses: actions/setup-node@v2
       with:
         node-version: ${{ matrix.node-version }}
+        cache: 'yarn'
     - run: yarn set version berry
     - run: yarn install
     - run: yarn coverage:check

Diff for: .github/workflows/test.yml

@@ -18,6 +18,7 @@ jobs:
     - uses: actions/setup-node@v2
       with:
         node-version: ${{ matrix.node-version }}
+        cache: 'yarn'
     - run: yarn set version berry
     - run: yarn -v
     - run: yarn install

Diff for: .gitignore

@@ -111,9 +111,14 @@ dist
 # Stores VSCode versions used for testing VSCode extensions
 .vscode-test
 
-# yarn v3
-.yarn/*
+# yarn v2, v3
 .pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/sdks
+!.yarn/versions
 
 # Scramjet framework specific
 build

Diff for: .yarn/plugins/@yarnpkg/plugin-echo-execute.cjs

@@ -0,0 +1,8 @@
+/* eslint-disable */
+module.exports = {
+name: "@yarnpkg/plugin-echo-execute",
+factory: function (require) {
+var plugin;(()=>{"use strict";var o={d:(t,e)=>{for(var r in e)o.o(e,r)&&!o.o(t,r)&&Object.defineProperty(t,r,{enumerable:!0,get:e[r]})},o:(o,t)=>Object.prototype.hasOwnProperty.call(o,t),r:o=>{"undefined"!=typeof Symbol&&Symbol.toStringTag&&Object.defineProperty(o,Symbol.toStringTag,{value:"Module"}),Object.defineProperty(o,"__esModule",{value:!0})}},t={};o.r(t),o.d(t,{default:()=>r});const e=require("@yarnpkg/core"),r={hooks:{wrapScriptExecution:async(o,t,r,a,n)=>async()=>(await e.StreamReport.start({configuration:t.configuration,json:!1,includeFooter:!1,stdout:n.stdout},async o=>{const r=e.formatUtils.applyColor(t.configuration,a,e.formatUtils.Type.NAME),i=e.formatUtils.applyColor(t.configuration,n.script,e.formatUtils.Type.CODE);o.reportInfo(e.MessageName.UNNAMED,`executing [${r}]: ${i}`)}),o())}};plugin=t})();
+return plugin;
+}
+};