Make a list of text insert tags used in email template files

[goddesswarship]

Email templates for Wildbook (/src/main/resources/emails/en) have tags that insert action-specific text to notify users of updates. We don't currently have a comprehensive list of these tags or which files they're pulling from. I've made a list of the ones I could find below, but there are likely more. Documenting these will help us with troubleshooting and fixing WildMeOrg/Wildbook#368

@ACCESSKEY@ (pardon the formatting; this was tagging a Github user without it)
@ADOPTION_CANCELLATION_LINK@
@ADOPTION_STRIPE_CUSTOMER_ID@
@CONTEXT_NAME@
@EMAIL_CONTENT@
@ENCOUNTER_COMMENTS@
@ENCOUNTER_DATE@
@ENCOUNTER_ID@
@ENCOUNTER_LINK@
@ENCOUNTER_LOCATION@
@ENCOUNTER_SEX@
@INDIVIDUAL_ALT_ID@
@INDIVIDUAL_ID@
@INDIVIDUAL_LINK@
@INDIVIDUAL_NICKNAME@
@LINK@ (pardon the formatting; this was tagging a Github user without it)
@REMOVEME_END@
@REMOVEME_LINK@
@REMOVEME_START@
@RESET_LINK@
@SENDER@ (pardon the formatting; this was tagging a Github user without it)
@TASKLINKS@
@TASKLINKSHTML@
@TEXT_CONTENT@
@USER@ (pardon the formatting; this was tagging a Github user without it)

[goddesswarship]

Per @TanyaStere42:

Hopefully I can get Jon to pull a list or source documentation for it, but that has to wait til after 10.3

[TanyaStere42]

I think this makes more sense under the wildbook-docs repo, since the end result is documentation

[goddesswarship]

Fixed! Thank you.