lint-staged  ^9.4.2  →  ^10.2.6

 eslint  ^6.6.0  →  ^7.1.0

 husky  ^3.0.9  →  ^4.2.5

 prettier  ^1.19.1  →  ^2.0.5

Update .prettierrc.json to ensure code style is still consistent.

Fix lint for new rule: space after function.

 @commitlint/cli                    ^8.2.0  →    ^8.3.5
 @commitlint/config-conventional    ^8.2.0  →    ^8.3.5
 @types/react                     ^16.9.11  →  ^16.9.35
 cross-env                          ^6.0.3  →    ^7.0.2
 dtslint                            ^2.0.0  →    ^3.6.4
 eslint-plugin-prettier             ^3.1.1  →    ^3.1.3
 mocha                              ^6.2.2  →    ^7.2.0
 nyc                               ^14.1.1  →   ^15.0.1
 preact                            ^10.0.4  →   ^10.4.4
 rimraf                             ^3.0.0  →    ^3.0.2

 rollup  ^1.26.3  →  ^1.32.1

Consolidate `build:min` and `build:unmin` into 1 `build` script.

Remove `cross-env` since NODE_ENV is no longer needed to
distinguish between builds.

In `rollup.config.js`, export both configs for minified and
unminified bundles.

Generate sourcemap for both builds (previously, sourcemap was
only generated for unmin or development bundle).