Fix blob enrichers initialization when WOPI is installed

Steps to reproduce

1. install the Nuxeo WOPI addon :

   nuxeoctl mp-install nuxeo-wopi

2. Set the WOPI properties in nuxeo.conf (the values are not important to reproduce)

   nuxeo.jwt.secret=xxx
   nuxeo.wopi.discoveryURL=https://onenote.officeapps.live.com/hosting/discovery
   nuxeo.wopi.baseURL=https://tech.com/nuxeo
   

3. Log in as Administrator
4. Navigate to the personal workspace
5. Upload a .docx file
6. Do a refresh of the page
7. Observe that the WOPI button is not displayed among the blob actions <== this is the bug
8. Navigate to the parent
9. Navigate back to the document
10. Observe that now the WOPI button is displayed among the blob actions

Analysis:

After doing a refresh, the "wopi" value is not passed to the "Enrichers-Blob" header => it's causing the bug

The "wopi" value is added by nuxeo-wopi.bundle.js.

        const a = window.Nuxeo || {};
        a.UI = a.UI || {},
        a.UI.config = a.UI.config || {},
        a.UI.config.enrichers = a.UI.config.enrichers || {},
        a.UI.config.enrichers.blob = a.UI.config.enrichers.blob || [],
        a.UI.config.enrichers.blob.push("wopi"); 

However it seems that this code is executed too late (= after the call to compute the enrichers)

From main.bundle.js:

                _loadDocument(e) {
                    return this.loading = !0,
                    this.docId = e.uid,
                    this.docPath = e.path,
                    this.$.doc.headers = this._computeHeaders(),
                    this.$.doc.enrichers = this._computeEnrichers(),