Twitter hashtag with starting numbers don't work

[andreslucena]

Describe the bug

As an administrator when I configure a process with a Twitter hashtag and this hashtag starts with numbers (for instance, #20BiennalEsplugues) the generated URL doesn't work.

To Reproduce
Steps to reproduce the behavior:

1. Sign in as admin
2. Edit a participatory process
3. Add #20BiennalEsplugues as hashtag.
4. Save
5. Go to frontend
6. Click in hashtag link
7. See error

Expected behavior
It should work

Extra data (please complete the following information):

• Decidim Version: 0.27.0.dev

Additional context

It's like this
https://twitter.com/hashtag/20BiennalEsplugues

It should be like this
https://twitter.com/search?q=%2320BiennalEsplugues&src=typed_query&f=top

Metadecidim proposal