ci: add build and format workflows

Signed-off-by: oppiliappan <[e-mail]>

.tangled/workflows/build.yml

···
+when:
+  - event: ["push"]
+    branch: ["master"]
+
+dependencies:
+  nixpkgs:
+    - go
+    - gcc
+
+environment:
+  CGO_ENABLED: 1
+
+steps:
+  - name: patch static dir
+    command: |
+       mkdir -p appview/pages/static; touch appview/pages/static/x
+
+  - name: build appview
+    command: |
+       go build -o appview.out ./cmd/appview
+
+  - name: build knot
+    command: |
+       go build -o knot.out ./cmd/knot

.tangled/workflows/fmt.yml

···
+when:
+  - event: ["push"]
+    branch: ["master"]
+
+dependencies:
+  nixpkgs:
+    - go
+    - alejandra
+
+steps:
+  - name: "nix fmt"
+    command: |
+       alejandra -c nix/**/*.nix flake.nix
+
+  - name: "go fmt"
+    command: |
+       gofmt -l .
+