chore: declare fonts via linaria global styles

it's handy because provides an ability to use theme constants.

src/components/GlobalStyles/fonts/Digital7Mono/index.ts

@@ -0,0 +1,12 @@
+import { css } from '@linaria/core'
+import { Digital7Mono } from '@/theme/fonts'
+
+void css`
+  @font-face {
+    font-family: ${Digital7Mono};
+    src: url('./digital-7mono.woff2') format('woff2');
+    font-weight: normal;
+    font-style: normal;
+    font-display: block;
+  }
+`

src/components/GlobalStyles/index.ts

@@ -1,9 +1,9 @@
 import { css } from '@linaria/core'
 import { dark1, white } from '@/theme/colors'
 import { darkScheme } from '@/theme/media'
-import './fonts/Digital7Mono/index.css'
+import './fonts/Digital7Mono'
 
-css`
+void css`
   :global() {
     html {
       -webkit-text-size-adjust: 100%;