Address SCSS warnings

[vytas7]

When running the page locally in the dev server, it results in many SCSS warnings along the lines of

WARNING in ./src/theme/theme.scss (./node_modules/css-loader/dist/cjs.js!./node_modules/sass-loader/dist/cjs.js!./src/theme/theme.scss)
Module Warning (from ./node_modules/sass-loader/dist/cjs.js):
Deprecation Warning on line 173, column 8 of file:///home/vytas/progs/falconry.github.io/node_modules/bootstrap/scss/_navbar.scss:173:8:
Sass's behavior for declarations that appear after nested
rules will be changing to match the behavior specified by CSS in an upcoming
version. To keep the existing behavior, move the declaration above the nested
rule. To opt into the new behavior, wrap the declaration in `& {}`.

More info: https://sass-lang.com/d/mixed-decls

173 |         flex-flow: row nowrap;

node_modules/bootstrap/scss/_navbar.scss 174:9             @content
node_modules/bootstrap/scss/mixins/_breakpoints.scss 65:5  media-breakpoint-up()
node_modules/bootstrap/scss/_navbar.scss 173:7             @import
node_modules/bootstrap/scss/bootstrap.scss 26:9            @import
src/theme/theme.scss 5:9                                   root stylesheet