Upgrade dependencies

[cquintana92]

This PR performs the following changes:

1. Upgrades some dependencies to the latest version.
2. Adapt the webpack.config.js to the upgrades. (mostly the CopyWebpackPlugin).
3. Upgrades the .jshintrc esversion (we were already using version 9 features and the IDE complained about it, so the only change it does is suppress these warnings).
4. Fix lint issues that arised due to (2).
5. Removed an unused and unmantained dependency (vue-textarea-autosize).

A dependency that could not be upgraded to the latest version is webpack (it has only been upgraded to v4), as some dependencies only support up to webpack 4, and crash if used with webpack v5.

There are still a few high severity vulns due to the aforementioned libs that only support webpack 4. They can be reviewed in the future.

λ npm audit
# npm audit report

glob-parent  <5.1.2
Severity: high
Regular expression denial of service in glob-parent - https://github.com/advisories/GHSA-ww39-953v-wcq6
fix available via `npm audit fix --force`
Will install webpack@5.72.1, which is a breaking change
node_modules/watchpack-chokidar2/node_modules/glob-parent
  chokidar  1.0.0-rc1 - 2.1.8
  Depends on vulnerable versions of glob-parent
  node_modules/watchpack-chokidar2/node_modules/chokidar
    watchpack-chokidar2  *
    Depends on vulnerable versions of chokidar
    node_modules/watchpack-chokidar2
      watchpack  1.7.2 - 1.7.5
      Depends on vulnerable versions of watchpack-chokidar2
      node_modules/watchpack
        webpack  4.44.0 - 4.46.0
        Depends on vulnerable versions of watchpack
        node_modules/webpack

5 high severity vulnerabilities

This PR closes:

• [Snyk] Upgrade bootstrap from 4.5.2 to 4.6.0 #110
• [Snyk] Upgrade webextension-polyfill from 0.6.0 to 0.8.0 #111
• [Snyk] Upgrade axios from 0.21.3 to 0.21.4 #112
• [Snyk] Upgrade vue-router from 3.5.2 to 3.5.3 #115
• [Snyk] Upgrade tippy.js from 6.3.2 to 6.3.4 #116
• Bump ajv from 6.10.2 to 6.12.6 #120
• Update packages. #124
• Bump yargs-parser from 13.1.1 to 13.1.2 #127
• Bump ejs from 2.7.4 to 3.1.7 #137

[nguyenkims]

LGTM, just left a question

[nguyenkims]

LGTM!