Build: Set more workflows as skip forks (origin only)

browsers jobs require BrowserStack sectrets and will fail otherwise,
which adds distraction to local commit histories.

.github/workflows/browsers-full.yaml

@@ -13,6 +13,7 @@ on:
 jobs:
   run:
     name: BrowserStack
+    if: github.repository == "qunitjs/qunit" # skip on forks
     runs-on: ubuntu-latest
     env:
       PUPPETEER_DOWNLOAD_PATH: ~/.puppeteer_download

.github/workflows/browsers-quick.yaml

@@ -5,6 +5,7 @@ on:
 jobs:
   run:
     name: BrowserStack
+    if: github.repository == "qunitjs/qunit" # skip on forks
     runs-on: ubuntu-latest
     env:
       PUPPETEER_DOWNLOAD_PATH: ~/.puppeteer_download

.github/workflows/doc-search.yaml

@@ -7,6 +7,7 @@ on:
 jobs:
   run:
     name: Update search index
+    if: github.repository == "qunitjs/qunit" # skip on forks
     runs-on: ubuntu-18.04
     steps:
       - uses: actions/checkout@v2

.github/workflows/spider-check.yaml

@@ -18,6 +18,7 @@ jobs:
     # Includes Python 3
     # https://github.com/actions/virtual-environments/blob/ubuntu20/20210318.0/images/linux/Ubuntu2004-README.md
     runs-on: ubuntu-latest
+    if: github.repository == "qunitjs/qunit" # skip on forks
     steps:
       - uses: actions/checkout@v2
         with: