Let the user group the skills with their desired categories

The current implementation uses some algorithm/calculation to group technical skills:
```
def make_skill_groups(
...
Group skills into categories.

Prioritizes small groups from unpopular labels to increases the likelihood
the large and popular labels can take the "leftovers".
```
I argue that A) this does not lead to standardization as it is a stochastic approach, and B) this leads to unwanted results. Regarding B, technical skills end up grouped under the same category (e.g. Tools), which might be outdated and hard to change (a PR is needed) . I suggest leaving the categorization to the user. The valid categories and skills are still the ones listed in the `tech_skills.toml` file.

Just an example:
```
Technical Skills
Web: HTML
Platforms: Docker, Google Firebase, Kubernetes, Linux
```
Let the user decide how to group these skills, e.g.
```
Technical Skills
Web: HTML
Cloud: Docker, Kubernetes, Google Firebase
Platforms: Linux

```