[FeatureRequest] Show time since an app was last updated by developer

Hi, while trying this nice app I found that it's missing an important essential feature. :slightly_smiling_face:

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### Why?
- **Conveys the likely state of a given project: whether it's maintained, updated for your Android version, security updates, feature parity, bug fixes etc.**
- Important context for comparing apps, at a glance. Easy to separate good and bad candidates.

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### F-Droid's situation:
- **Shows this information on an app's page. For this reason alone, I use F-Droid for searching.**

### Droid-ify's current situation:
- **Lacks the feature**
- **Sometimes, you can look up the information if there's version history. It's not a good work-around:**
- **Unreliable:** Version history is not always present.
- **Time-consuming and tedious:** going back and forth (while stacking up various information in your head for comparison). If a feature is tedious or hidden away, users just avoid it altogether as people seek the path of least resistance.
- **Date is not in [ISO 8601 format](https://en.wikipedia.org/wiki/ISO_8601):** Is confusing for EU users (US format can be misinterpreted: month and day are swapped, not chronologically formatted).

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### Proposed solution:
- **Show relative time since last update for each respective app. Implemented in the following places (in order of priority):**
- **1. In search results:** _e.g. "14m" or "14 months"_.
- If there's a desire for polishing (not a priority), text can be accompanied by an icon. For consistency the icon should correlate with the icon used for "sort by update recency".
- If necessary due to horisontal space limitation, it should replace version number. Version number is arbitrary information for a user. Its usefulness is low without the context of the respective app's versioning system and version history. Time since last update is more useful.
- **2. In app page:** _e.g. "Last updated 14 months ago"_.
- **3. In categories/manual navigation:** The same benefits applies here.
- **4. In "installed apps list":**
- Useful for quickly identifying old apps that are no longer updated or no longer wanted.
- As apps pile up, it can be daunting to go through them to tidy up. So people tend to let the mess pile up.
- Can be useful identifying repositories which are either deprecated or outdated.

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If there's something you want me to clarify, improve upon or reformat I'll be happy to make changes to the issue. :slightly_smiling_face: