Fix regression of not being able to search in the address bar anymore (#62)

- Added different search modes in the options:
- Result must contain the exact search phrase
- Result must contain all words of the search phrase, but in any order (this is the new default)
- Result must contain at least one of the words in the search phrase (#57)
- Result must match the regular expression search
- Added an export feature as wished in #55. I was not able to reproduce the reporter's problem though, so I don't see a use case for the export
- Export a default bookmark HTML format that can be imported into any browser
- Export a JSON document similar to the pinboard export over at [pinboard's backup page](https://pinboard.in/settings/backup)
- Optimised some code causing API calls to sometimes be fired twice
- Technical changes
- Optimised how the different files / modules reference each other
- Updated dependencies
- Switched from tslint to eslint
- Shrank the 16-pixel icon to actually be 16 pixels wide

#### v1.4.1
- Fixed pagination in popup

#### v1.4.0
- Added prettier dark mode and option to use browser/system setting for the dark mode, see [MDN](https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme).
- (#51) Adds keybind Alt+Shift+P to open the create bookmark dialog within the popup ([Firefox only](https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/browserAction/openPopup))
- (#51) Adds keybind Alt+Shift+Left to open the sidebar (Firefox only)
- (#50) Fixes search prefixing and makes search the same across popup, sidebar and browser address bar
- (#49) Improves tag suggestions when adding a new bookmark

- Added prettier dark mode and option to use browser/system setting for the dark mode, see [MDN](https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme).
- (#51) Adds keybind Alt+Shift+P to open the create bookmark dialog within the popup ([Firefox only](https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/browserAction/openPopup))
- (#51) Adds keybind Alt+Shift+Left to open the sidebar (Firefox only)
- (#50) Fixes search prefixing and makes search the same across popup, sidebar and browser address bar
- (#49) Improves tag suggestions when adding a new bookmark

- Merged pull request #48, thanks @marcinsmialek! This adds the keyboard shortcut Alt-P (by default) to open the pinboard popup. Also, it fixes the behaviour when searching for bookmarks in the omnibar when no results are found.
- On development side: updated dependencies. Did not replace tslint by eslint yet because it seems to be quite the task...

* Added keyboard controls for the popup (not 100% functioning yet)
* Made options screen a bit clearer
* Fixed bugs
* Introduced bugs, probably.

Fixed stupid typo causing bookmarks to not sync.

* Adds customisable colours: Set the addon to dark mode, light mode, or any colour scheme your heart desires
* **Firefox only**: Adds a sidebar containing a searchable list of all your bookmarks.
* Updates icons in the popup
* Backend stuff:
* Updated to v1.2.0 of Mozilla's webextension-polyfill
* Streamlined some more code
* The icons were unicode characters before, now they are embedded SVG
* Moved the filter functionality into appropriate class to try and reduce code duplication
* Made background scripts not persistent (https://developer.chrome.com/extensions/event_pages)

Fixes a bug causing the "shared by default" option not to persist
Fixes an oversight causing the regex not to be added to the direct "pin current page" button.

v1.2.6 - v1.2.9:
Adds the option to run a regex on the tab title (might be useful when using an addon to modify the tab title). Thanks @alerque for the suggestion (see #25)!
Adds css scaling on the popup for firefox when using two screens with different DPI (see issue #3)
Updates the timeout increase to introduce a maximum timeout of 10 minutes
Adds badges to the button to show when a connection issue occurs
Fixes a bug causing high CPU load when addon options are missing
Misc. stuff, check the commits if you are interested, nothing worth mentioning

This version addresses the scaling issue of the popup when using two screens with different DPI settings, but it does not solve it entirely (subject to a Firefox bug unfortunately).

v1.2.1 - v1.2.5:

Adds symbol in popup for shared bookmarks
Adds filter in popup for bookmarks flagged as "to read"
Optimized API request queue (deleting duplicates)
Added API polling to check every 5 minutes for new bookmarks

* Adds checking pinboard for updates in 5 minute intervals in the background
* Bugfixes
* Internal code restructuring to use await/async

* Added option to auto-save new bookmarks to Pinboard
* Added option to clear the API key
* Added option to force-reload the pins
* Improved design of the popup
* Made extension Google-Chrome compatible
* Changed Icon slightly
* Bugfixes
* Added new bugs probably