Automate khoj.el testing using Github workflow

Install transient.el dependency as it is not available by default
before Emacs 28.1

.github/workflows/test_khoj_el.yml

@@ -0,0 +1,49 @@
+name: test khoj.el
+
+on:
+  push:
+    branches:
+      - 'master'
+    paths:
+      - src/interface/emacs/*.el
+      - src/interface/emacs/tests/*.el
+      - .github/workflows/test_khoj_el.yml
+  pull_request:
+    branches:
+      - 'master'
+    paths:
+      - src/interface/emacs/*.el
+      - src/interface/emacs/tests/*.el
+      - .github/workflows/test_khoj_el.yml
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        emacs_version:
+          - 27.1
+          - 27.2
+          - 28.1
+          - 28.2
+          - snapshot
+    steps:
+      - uses: purcell/setup-emacs@master
+        with:
+          version: ${{ matrix.emacs_version }}
+      - uses: actions/checkout@v3
+      - name: Test Khoj.el
+        run: |
+           # Run ERT tests on khoj.el
+           emacs -batch \
+           --eval "(progn \
+                    (require 'package) \
+                    (push '(\"melpa\" . \"https://melpa.org/packages/\") package-archives) \
+                    (package-initialize) \
+                    (unless package-archive-contents (package-refresh-contents)) \
+                    (unless (package-installed-p 'transient) (package-install 'transient)))" \
+           -l ert \
+           -l ./src/interface/emacs/khoj.el \
+           -l ./src/interface/emacs/tests/khoj-tests.el \
+           -f ert-run-tests-batch-and-exit