Formatted with config file and adding format check

* Added format file .JuliaFormatter
* Added GitHub Action for format checking
* Formatted the code with the file above and some hand tweaks on
comments

.JuliaFormatter.toml

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+align_assignment = true
+align_conditional = true
+align_matrix = true
+align_pair_arrow = true
+align_struct_field = true
+always_for_in = true
+always_use_return = true
+annotate_untyped_fields_with_any = false
+conditional_to_if = true
+for_in_replacement = "∈"
+format_docstrings = true
+import_to_using = true
+indent = 4
+indent_submodule = true
+join_lines_based_on_source = true
+long_to_short_function_def = true
+margin = 88
+normalize_line_endings = "unix"
+pipe_to_function_call = true
+remove_extra_newlines = true
+separate_kwargs_with_semicolon = true
+surround_whereop_typeparameters = true
+trailing_comma = true
+whitespace_in_kwargs = false
+whitespace_ops_in_indices = false
+whitespace_typedefs = true
+yas_style_nesting = true

.github/workflows/format_check.yml

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+name: Format Check
+
+on:
+  push:
+    branches: ["master", "dev", "format"]
+  pull_request:
+    branches: ["master", "dev"]
+jobs:
+  check:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        julia-version: [1.9.3]
+        julia-arch: [x86]
+        os: [ubuntu-latest]
+    steps:
+      - uses: julia-actions/setup-julia@latest
+        with:
+          version: ${{ matrix.julia-version }}
+
+      - uses: actions/checkout@v1
+      - name: Install JuliaFormatter and format
+        run: |
+          julia  -e 'using Pkg; Pkg.add(PackageSpec(name="JuliaFormatter"))'
+          julia  -e 'using JuliaFormatter; format(".", verbose=true)'
+      - name: Format check
+        run: |
+          julia -e '
+          out = Cmd(`git diff --name-only`) |> read |> String
+          if out == ""
+              exit(0)
+          else
+              @error "Some files have not been formatted !!!"
+              write(stdout, out)
+              exit(1)
+          end'