Add html macro open tag parse tag (#198)

This commit adds a test to the `html-macro`.

The test verifies that we parse opening tags correctly, such as
```
<div id="hello">
```

This test was introduced to help others understand how to test the
macro's internals.
Being able to test the more complex aspects of the macro's internals
helps with getting quicker feedback when working on the internals.

.github/workflows/ci-tests.yml

@@ -11,41 +11,39 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v1
-    - uses: actions-rs/cargo@v1
+      - uses: actions/checkout@v2
 
-    - name: Latest Rust Nightly
-      uses: actions-rs/toolchain@v1
-      with:
+      - uses: actions-rs/toolchain@v1
+        with:
           toolchain: nightly
           override: true
           # Used when testing with `wasm-pack test`
           target: wasm32-unknown-unknown
 
-    - name: Rust Version Info
-      run: rustc --version && cargo --version && echo $CARGO_HOME
-
-    - name: Install wasm-pack
-      run: >
-            curl -L https://github.com/rustwasm/wasm-pack/releases/download/v0.10.0/wasm-pack-v0.10.0-x86_64-unknown-linux-musl.tar.gz
-            | tar --strip-components=1 --wildcards -xzf - "*/wasm-pack"
-            && chmod +x wasm-pack
-            && mv wasm-pack $HOME/.cargo/bin/
-
-    - name: Browser versions
-      run: wasm-pack --version && firefox --version
-
-    - uses: actions/cache@v2
-      with:
-        path: |
-          ~/.cargo/registry
-          ~/.cargo/git
-          target
-        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
-
-    - name: Run all tests
-      run: ./test.sh
-
-    # NOTE: We can start running the full test suite on stable after https://github.com/rust-lang/rust/issues/54725
-    - name: Check that Stable can compile
-      run: cargo +stable check --all
+      - name: Rust Version Info
+        run: rustc --version && cargo --version && echo $CARGO_HOME
+
+      - name: Install wasm-pack
+        run: >
+          curl -L https://github.com/rustwasm/wasm-pack/releases/download/v0.10.0/wasm-pack-v0.10.0-x86_64-unknown-linux-musl.tar.gz
+          | tar --strip-components=1 --wildcards -xzf - "*/wasm-pack"
+          && chmod +x wasm-pack
+          && mv wasm-pack $HOME/.cargo/bin/
+
+      - name: Browser versions
+        run: wasm-pack --version && firefox --version
+
+      - uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+
+      - name: Run all tests
+        run: ./test.sh
+
+      # NOTE: We can start running the full test suite on stable after https://github.com/rust-lang/rust/issues/54725
+      - name: Check that Stable can compile
+        run: cargo +stable check --all